It's nice to see DataChasers on the list -- it's both one of my favorites and one of the very best. I can think of several more greats that are not on the list. Like its excellent spinoff/prequel, LunaStar.

I post a link to all of these comics with every update of my comic (none are mine, I just like 'em):
The Adventures of Jonas might be the best comic I've ever read.
Civilian, a cool "real-world" supero comic.
Genocide Man, a Warren Ellis-y webcomic better than Warren Ellis' actual webcomic.
Kay & P, wonderfully oddball yet very moving.
Lavender Legend, a delightful gender-bending adventure.
Let It Ride, just damn funny.
Mars II, dark brilliant sci-fi.
My Life With Fel, like a Saturday morning cartoon for grownups, brilliant art.
Oi! Tales of Bardic Fury, imaginative faux-history with cool art.
Pulse, my favorite superhero comic.
Twilight Trust, funny, smart adventure/monster fighting.
Zelfia, my favorite fantasy webcomic, very Whedon-y.

P.S. Mine is Eternal Knights, a superhero/fantasy comic about a suicidal immortal.