El Goonish Shive. Be warned, the comic's been around for over 10 years. That's a lot of strips to catch up on.
Order of the Stick, on occasion. I keep falling behind, forgetting where I was, and needing to start over, though.
Looking for Group, on occasion. See OotS.
8 Bit Theater. I really need to get back to reading that, now that the story is finished.
Last Res0rt. This is my number one webcomic that I currently read. It defies any set genre, but the closest I can think of to identify it is "furry cyberpunk". That's "furry" as in "anthropomorphic", mind you. It's has a dark feel, but the art is rather bright. If you enjoy cyberpunk, and aren't set off by the description I gave, I'd check it out.
Mind you, with Last Res0rt and El Goonish Shive, the art starts off pretty bad. It gets better if you stick it out. Takes longer with EGS than it does with Last Res0rt, though.