Regularly updated

•  xkcd
•  cyanide&happines
•  http://smbc-comics.com
•  http://www.nataliedee.com/
•  http://www.toothpastefordinner.com/
•  http://www.somethingofthatilk.com/
•  http://invisiblebread.com/
•  http://twokinds.keenspot.com/
•  http://www.sinfest.net/
•  http://www.bugcomic.com
•  http://www.johnnywander.com/
•  http://cowbirdsinlove.com
•  http://buttersafe.com/
•  http://nerfnow.com/
•  http://nedroid.com/
•  http://www.lefthandedtoons.com/
•  http://www.catandgirl.com/
•  http://dresdencodak.com/
•  http://explodingdog.com/
•  http://www.mspaintadventures.com/
•  http://overcompensating.com/
•  http://fanboys-online.com/
•  http://threepanelsoul.com/
•  http://www.amazingsuperpowers.com/
•  http://www.dieselsweeties.com/
•  http://www.awkwardzombie.com
•  http://www.somethingpositive.net/
•  http://leasticoulddo.com/
•  http://www.picturesforsadchildren.com/
•  http://www.stationv3.com/
•  http://alienlovespredator.com/
•  http://oglaf.com (adult)
•  http://www.c.urvy.org/ (adult)

Occasionally updated or finsihed

•  http://www.therobotissad.com/ and  http://zhongda.comicgenesis.com/ by Tam Nguyen
•  http://www.kiwisbybeat.com/ especially 'Minus'
•  http://909sickle.com/
•  http://userfriendly.org
•  http://pbfcomics.com/
•  http://www.graphicsmash.com/comics/og.php
•  http://www.decorumcomics.com/
•  http://dragonandtiger.blogspot.com/
•  http://girlyyy.com/go/1
•  http://tile.comicgenesis.com/

Untested

These seem interesting, but I didn't really have time to read them yet.

•  http://satwcomic.com/
•  http://www.tomgauld.com/
•  http://www.viruscomix.com/
•  http://rockpapercynic.com/
•  http://www.thedevilbear.com/
•  http://doctorcatmd.com/
•  http://poorlydrawnlines.com/