Penny Arcade	Veterans of the webcomic business, Jerry "Tycho" Holkins and Mike "Gabe" Krahulik take no prisoners, if games of any kind are concerned.
Mega Tokyo	Part melancholic, part wacky, and drawn in best "American Manga" style.
Dilbert	Scott Adams is well-known for drawing the truth and nothing but it in his daily newspaper strip about work in today's companies.
Real Life	Another renowned webcomic, a mix of satire and soap opera.
PVP	Scott Kurtz' classic daily comic strip - kinda like Garfield back in his good days.
Mac Hall	Although done by Apple freaks, still highly enjoyable. Oh, and great coloring, too.
VG Cats	Umm, yeah. That's what happens when video games meet designer drugs, I suppose. Still extremely funny, sometimes.
Nicht Lustig	If you understand German, you owe it to yourself to read this German daily strip. Highly recommended.
Chugworth Academy	Strange humor, but very well drawn and the source of some real classics (like "Ryo and the women")
Wapsi Square	Nice comic strip, co-starring Tepoztecal, the Aztec God of alcohol!
Sore Thumbs	The adventures of a far-out right-wing mama's boy, his ultra-liberal sister, a literally dickless Ex-G.I. and his mascot midget bear, running a video game shop.
The noob	Excellent collection of role-playing clichés, comic style.
Happy Tree Friends	Not very nice and not very funny (after watching several episodes), but you should at least know about it.
August Strindberg & Helium	Dead site, but what the hell. Strindberg and Helium are like Markus and Peter, squared.