Okay, since my first post disappeared, I'll try again:
Most webcomics suck ass, but so does most of everything else, and there are a few good ones in there, as well as a few guilty pleasures.
Here are the ones that are REALLY good:
xkcd [http://xkcd.com/] (pure nerd humor at its finest. The jokes are hit-and-miss, but the ones that hit... hit HARD)
Misfile [http://www.misfile.com/] (a comic so brilliantly written and illustrated it shouldn't even be on the web. It's drawn in manga style but it's got nothing to do with anime)
Venus Envy [http://venusenvy.comicgenesis.com/] (a funny, sad, scary, touching, goofy and heartfelt tale with a social conscience)
And there are the ones that are probably, in perspective, not all that great but I love 'em anyway:
VG Cats [http://www.vgcats.com/] (for fairly obvious reasons)
The Wotch [http://www.thewotch.com/] (*sigh* I can't really defend this one, but what it does, it does well)
El Goonish Shive [http://www.egscomics.com/] (on the rare occasions when Dan actually updates)
I absolutely despise CAD and C&H, though. *ducks flying objects*