What third-party ASP.NET controls or libraries can you not live without?
<p>I am working on a project right now, and I have a few must-have controls that I include in most sites I build. Often times it strikes me that the best controls are not always that well publicized so I thought I would ask the Stack Overflow community about their favorite third-party ASP.NET controls - the ones you just have to have on a project because they are so valuable.</p>

<p>EDIT:</p>

<p>Some people have asked for clarification and the controls that I include.</p>

<p>First, I am not talking about just user interface controls but libraries as well, a few people have mentioned <a href="http://en.wikipedia.org/wiki/Log4j#Ports" rel="nofollow">log4net</a> which falls into this category.</p>

<p>For me, there is one third-party control package which I find to be masterfully done and an incredible value for the money - it is Peter Blum's Data Entry Suite. As Scott Hanselman says, it is a "complete re-imagining of the ASP.NET Validation framework" and it is loaded with controls for rich interaction with data entry forms.</p>

<p>Outside of that, I am really digging <a href="http://en.wikipedia.org/wiki/JQuery" rel="nofollow">jQuery</a> lately but like most of the answers so far also use the ASP.NET Ajax Control Toolkit in many places.</p>
