Is there a list on the web where I can find Cantonese special characters and their meaning?
You can check out wikipedia's page for Written Cantonese which contains a lot of information like borrowed characters, marked phonetic loans and workarounds but the page I'm guessing you're looking, mostly, for is derived characters which contains things like:

冇 móuh (v. not have). Originally 無. Standard written Mandarin: 沒有
係 haih (v. be). Standard written Mandarin: 是
佢 kéuih (pron. he/she/it). Originally 渠. Standard written Mandarin: 他, 她, 它, 牠, 祂
乜 māt (pron. what) often followed by 嘢 to form 乜嘢. Originally 物也. Standard written Mandarin: 什麼