user1398: Continuing on the tradition, let us tag as many series as possible, so that new users can find the tags easily without having to dabble with retag workaround.
For  people new to this, check out the rationale here.
Previous posts in the series:

Fall 2014 series tags
Winter 2015 series tags
Spring 2015 series tags

What series are airing in Summer 2015, and which have tags?

user1398: I use the names from neregate, adding a few missing series from anichart. Feel free to make improvements and update the post as it goes.
Leftover from Spring season

Arslan Senki arslan-senki
Baby Steps 2
Denpa Kyoushi denpa-kyoushi
Eikoku Ikke, Nihon o Taberu
Kyoukai no Rinne kyoukai-no-rinne
Nagato Yuki-chan no Shoushitsu nagato-yuki-chan
Ninja Slayer From Animation ninja-slayer
Ore Monogatari!!
Shoukugeki no Souma shokugeki-no-soma

Summer series

Akagami no Shirayuki-hime
Aoharu x Kikanjuu
Aquarion Logos
Chaos Dragon: Sekiryuu Sen'eki
Charlotte charlotte
Chu Feng: BEE
Classroom Crisis
Dragon Ball Super dragon-ball
Durarara!! x2 Ten durarara
Fate/kaleid liner Prisma Illya 2wei Herz! fate-kaleid-liner
Gakkou Gurashi gakkou-gurashi
Gangsta.
Gatchaman Crowds insight gatchaman-crowds
Gate: Jietai Kanochi nite, Kaku Tatakaeri gate
God Eater god-eater
Himouto! Umaru-chan himouto-umaru-chan
Jitsu wa Watashi wa
Joukamachi no Dandelion joukamachi-no-dandelion
Junjou Romantica 3
Kangoku Gakuen
Kuusen Madoshi Kouhosei no Kyoukan sky-wizards-academy
Monster Musume no Iru Nichijou monmusu
Non Non Biyori Repeat non-non-biyori
Overlord overlord
Ranpo Kitan: Game of Laplace ranpo-kitan
Rokka no Yuusha rokka-no-yuusha
Senki Zesshou Symphogear GX senki-zesshou-symphogear
Shimoneta to Iu Gainen ga Sonzai Shinai Taikutsu na Sekai shimoseka
Sore ga Seiyuu!
The IDOLM@STER Cinderella Girls Second Season the-idolmaster
To Love-Ru -Trouble- Darkness 2nd to-love-ru
Ushio to Tora ushio-to-tora
Venus Project
Working!!! working

Shorts

Bikini Warriors
Danchigai
Hetalia: The World Twinkle
Kaijuu Sakaba Kanpai!
Kurayami Santa
Makura no Danshi
Million Doll
Miss Monochrome Second Season miss-monochrome
Okusama ga Seito Kaichou!
Q Transformers: Kaettekita Convoy no Nazo 2
Suzakinishi: The Animation
Teekyuu 5 teekyuu
Wakaba * Girl
Wakako-Zake
Wooser no Sono Higurashi Mugen-hen


1398: <p>Continuing on the tradition, let us tag as many series as possible, so that new users can find the tags easily without having to dabble with <a href="https://anime.stackexchange.com/questions/tagged/retag" class="post-tag" title="show questions tagged &#39;retag&#39;" rel="tag">retag</a> workaround.</p>

<p>For  people new to this, <a href="https://anime.meta.stackexchange.com/questions/1126/">check out the rationale here</a>.</p>

<p>Previous posts in the series:</p>

<ul>
<li><a href="https://anime.meta.stackexchange.com/questions/1126/">Fall 2014 series tags</a></li>
<li><a href="https://anime.meta.stackexchange.com/questions/1191/">Winter 2015 series tags</a></li>
<li><a href="https://anime.meta.stackexchange.com/questions/2303/">Spring 2015 series tags</a></li>
</ul>

<p><strong>What series are airing in Summer 2015, and which have tags?</strong></p>
 1398: <p>I use the names from <a href="http://static.neregate.com/2015/05/neregate.com-Summer-2015-Anime-Chart-v2.jpg" rel="nofollow noreferrer">neregate</a>, adding a few missing series from <a href="http://anichart.net/summer" rel="nofollow noreferrer">anichart</a>. Feel free to make improvements and update the post as it goes.</p>

<h2>Leftover from Spring season</h2>

<ul>
<li><strong>Arslan Senki</strong> <a href="https://anime.stackexchange.com/questions/tagged/arslan-senki" class="post-tag" title="show questions tagged &#39;arslan-senki&#39;" rel="tag">arslan-senki</a></li>
<li><strong>Baby Steps 2</strong></li>
<li><strong>Denpa Kyoushi</strong> <a href="https://anime.stackexchange.com/questions/tagged/denpa-kyoushi" class="post-tag" title="show questions tagged &#39;denpa-kyoushi&#39;" rel="tag">denpa-kyoushi</a></li>
<li><strong>Eikoku Ikke, Nihon o Taberu</strong></li>
<li><strong>Kyoukai no Rinne</strong> <a href="https://anime.stackexchange.com/questions/tagged/kyoukai-no-rinne" class="post-tag" title="show questions tagged &#39;kyoukai-no-rinne&#39;" rel="tag">kyoukai-no-rinne</a></li>
<li><strong>Nagato Yuki-chan no Shoushitsu</strong> <a href="https://anime.stackexchange.com/questions/tagged/nagato-yuki-chan" class="post-tag" title="show questions tagged &#39;nagato-yuki-chan&#39;" rel="tag">nagato-yuki-chan</a></li>
<li><strong>Ninja Slayer From Animation</strong> <a href="https://anime.stackexchange.com/questions/tagged/ninja-slayer" class="post-tag" title="show questions tagged &#39;ninja-slayer&#39;" rel="tag">ninja-slayer</a></li>
<li><strong>Ore Monogatari!!</strong></li>
<li><strong>Shoukugeki no Souma</strong> <a href="https://anime.stackexchange.com/questions/tagged/shokugeki-no-soma" class="post-tag" title="show questions tagged &#39;shokugeki-no-soma&#39;" rel="tag">shokugeki-no-soma</a></li>
</ul>

<h2>Summer series</h2>

<ul>
<li><strong>Akagami no Shirayuki-hime</strong></li>
<li><strong>Aoharu x Kikanjuu</strong></li>
<li><strong>Aquarion Logos</strong></li>
<li><strong>Chaos Dragon: Sekiryuu Sen'eki</strong></li>
<li><strong>Charlotte</strong> <a href="https://anime.stackexchange.com/questions/tagged/charlotte" class="post-tag" title="show questions tagged &#39;charlotte&#39;" rel="tag">charlotte</a></li>
<li><strong>Chu Feng: BEE</strong></li>
<li><strong>Classroom Crisis</strong></li>
<li><strong>Dragon Ball Super</strong> <a href="https://anime.stackexchange.com/questions/tagged/dragon-ball" class="post-tag" title="show questions tagged &#39;dragon-ball&#39;" rel="tag">dragon-ball</a></li>
<li><strong>Durarara!! x2 Ten</strong> <a href="https://anime.stackexchange.com/questions/tagged/durarara" class="post-tag" title="show questions tagged &#39;durarara&#39;" rel="tag">durarara</a></li>
<li><strong>Fate/kaleid liner Prisma Illya 2wei Herz!</strong> <a href="https://anime.stackexchange.com/questions/tagged/fate-kaleid-liner" class="post-tag" title="show questions tagged &#39;fate-kaleid-liner&#39;" rel="tag">fate-kaleid-liner</a></li>
<li><strong>Gakkou Gurashi</strong> <a href="https://anime.stackexchange.com/questions/tagged/gakkou-gurashi" class="post-tag" title="show questions tagged &#39;gakkou-gurashi&#39;" rel="tag">gakkou-gurashi</a></li>
<li><strong>Gangsta.</strong></li>
<li><strong>Gatchaman Crowds insight</strong> <a href="https://anime.stackexchange.com/questions/tagged/gatchaman-crowds" class="post-tag" title="show questions tagged &#39;gatchaman-crowds&#39;" rel="tag">gatchaman-crowds</a></li>
<li><strong>Gate: Jietai Kanochi nite, Kaku Tatakaeri</strong> <a href="https://anime.stackexchange.com/questions/tagged/gate" class="post-tag" title="show questions tagged &#39;gate&#39;" rel="tag">gate</a></li>
<li><strong>God Eater</strong> <a href="https://anime.stackexchange.com/questions/tagged/god-eater" class="post-tag" title="show questions tagged &#39;god-eater&#39;" rel="tag">god-eater</a></li>
<li><strong>Himouto! Umaru-chan</strong> <a href="https://anime.stackexchange.com/questions/tagged/himouto-umaru-chan" class="post-tag" title="show questions tagged &#39;himouto-umaru-chan&#39;" rel="tag">himouto-umaru-chan</a></li>
<li><strong>Jitsu wa Watashi wa</strong></li>
<li><strong>Joukamachi no Dandelion</strong> <a href="https://anime.stackexchange.com/questions/tagged/joukamachi-no-dandelion" class="post-tag" title="show questions tagged &#39;joukamachi-no-dandelion&#39;" rel="tag">joukamachi-no-dandelion</a></li>
<li><strong>Junjou Romantica 3</strong></li>
<li><strong>Kangoku Gakuen</strong></li>
<li><strong>Kuusen Madoshi Kouhosei no Kyoukan</strong> <a href="https://anime.stackexchange.com/questions/tagged/sky-wizards-academy" class="post-tag" title="show questions tagged &#39;sky-wizards-academy&#39;" rel="tag">sky-wizards-academy</a></li>
<li><strong>Monster Musume no Iru Nichijou</strong> <a href="https://anime.stackexchange.com/questions/tagged/monmusu" class="post-tag" title="show questions tagged &#39;monmusu&#39;" rel="tag">monmusu</a></li>
<li><strong>Non Non Biyori Repeat</strong> <a href="https://anime.stackexchange.com/questions/tagged/non-non-biyori" class="post-tag" title="show questions tagged &#39;non-non-biyori&#39;" rel="tag">non-non-biyori</a></li>
<li><strong>Overlord</strong> <a href="https://anime.stackexchange.com/questions/tagged/overlord" class="post-tag" title="show questions tagged &#39;overlord&#39;" rel="tag">overlord</a></li>
<li><strong>Ranpo Kitan: Game of Laplace</strong> <a href="https://anime.stackexchange.com/questions/tagged/ranpo-kitan" class="post-tag" title="show questions tagged &#39;ranpo-kitan&#39;" rel="tag">ranpo-kitan</a></li>
<li><strong>Rokka no Yuusha</strong> <a href="https://anime.stackexchange.com/questions/tagged/rokka-no-yuusha" class="post-tag" title="show questions tagged &#39;rokka-no-yuusha&#39;" rel="tag">rokka-no-yuusha</a></li>
<li><strong>Senki Zesshou Symphogear GX</strong> <a href="https://anime.stackexchange.com/questions/tagged/senki-zesshou-symphogear" class="post-tag" title="show questions tagged &#39;senki-zesshou-symphogear&#39;" rel="tag">senki-zesshou-symphogear</a></li>
<li><strong>Shimoneta to Iu Gainen ga Sonzai Shinai Taikutsu na Sekai</strong> <a href="https://anime.stackexchange.com/questions/tagged/shimoseka" class="post-tag" title="show questions tagged &#39;shimoseka&#39;" rel="tag">shimoseka</a></li>
<li><strong>Sore ga Seiyuu!</strong></li>
<li><strong>The IDOLM@STER Cinderella Girls Second Season</strong> <a href="https://anime.stackexchange.com/questions/tagged/the-idolmaster" class="post-tag" title="show questions tagged &#39;the-idolmaster&#39;" rel="tag">the-idolmaster</a></li>
<li><strong>To Love-Ru -Trouble- Darkness 2nd</strong> <a href="https://anime.stackexchange.com/questions/tagged/to-love-ru" class="post-tag" title="show questions tagged &#39;to-love-ru&#39;" rel="tag">to-love-ru</a></li>
<li><strong>Ushio to Tora</strong> <a href="https://anime.stackexchange.com/questions/tagged/ushio-to-tora" class="post-tag" title="show questions tagged &#39;ushio-to-tora&#39;" rel="tag">ushio-to-tora</a></li>
<li><strong>Venus Project</strong></li>
<li><strong>Working!!!</strong> <a href="https://anime.stackexchange.com/questions/tagged/working" class="post-tag" title="show questions tagged &#39;working&#39;" rel="tag">working</a></li>
</ul>

<h2>Shorts</h2>

<ul>
<li><strong>Bikini Warriors</strong></li>
<li><strong>Danchigai</strong></li>
<li><strong>Hetalia: The World Twinkle</strong></li>
<li><strong>Kaijuu Sakaba Kanpai!</strong></li>
<li><strong>Kurayami Santa</strong></li>
<li><strong>Makura no Danshi</strong></li>
<li><strong>Million Doll</strong></li>
<li><strong>Miss Monochrome Second Season</strong> <a href="https://anime.stackexchange.com/questions/tagged/miss-monochrome" class="post-tag" title="show questions tagged &#39;miss-monochrome&#39;" rel="tag">miss-monochrome</a></li>
<li><strong>Okusama ga Seito Kaichou!</strong></li>
<li><strong>Q Transformers: Kaettekita Convoy no Nazo 2</strong></li>
<li><strong>Suzakinishi: The Animation</strong></li>
<li><strong>Teekyuu 5</strong> <a href="https://anime.stackexchange.com/questions/tagged/teekyuu" class="post-tag" title="show questions tagged &#39;teekyuu&#39;" rel="tag">teekyuu</a></li>
<li><strong>Wakaba * Girl</strong></li>
<li><strong>Wakako-Zake</strong></li>
<li><strong>Wooser no Sono Higurashi Mugen-hen</strong></li>
</ul>
