[Ravager]

I'll add a few more:

Sluggy Freelance:
www.sluggy.com

A long plotline woth comics released every day for the last 8 years I think. Well worth going through though.

The Last Days of Foxhound:
http://www.gigaville.com/listcomic.php

Based on the Metal Gear series, though mostly understandable if you haven't played the games (like I haven't)

D&D based comics:
http://thunt.comicgen.com/ - Goblins - Sometimes quite gory, but otherwise good -especially if you understand the D&D references
http://www.thenoobcomic.com/index.html - Parody of MMORPG's.
http://www.seraph-inn.com - Inverloch -A very well-drawn comic/story, definitely worth looking at and not specifically D&D (e.g. fantasy style but not D&D set)
http://www.giantitp.com/cgi-bin/GiantITP/ootscript - The Order of the Stick - Heavy on D&D references but a good storyline.

Right, that should be enough to keep everyone going for a while.