MegaTokyo. It simply doesn't get any better than this.
8-Bit Theatre. It's a great comic for anyone who played/loved the original Final Fantasy.
Little Gamers. A great comic. What more needs be said?
User Friendly. Sure, it's not as great or weird as some of the others, but it is daily and has its moments.
And of course there are the profesional comics:
Cats with Hands
Close to Home
For Better Or Worse (sometimes)
Frank and Earnest
Rhymes with Orange
Rose is Rose
And to think, I used to read a lot more. I've trimmed the list down quite a bit.