Ok...hadn't got this far in the forum, and figured I should add my list. Anyway, these are the ones I have bookmarked on the puter:
http://xkcd.com/ One of the first ones recommended to me, and I admit I don't get every one, but the creativity is amazing.
http://twolumps.net/ Meaningful to me because (a) it's often very funny and (b) our first cat as a couple was a Russian Blue, the cats featured in this comic.
http://questionablecontent.net/ But of course ... followed this one after all the mentions by David Willis, and very glad I did.
http://thebookofbiff.com/ A nicely warped sense of humor.
http://www.ma3comic.com The naughtiest comic I read, although Willis may change that. I'm too cheap to find out.
http://www.dumbingofage.com/ With, of course, Shortpacked! (I found that because of a For Better Or For Worse group on Live Journal I read - DON"T JUDGE ME YOU HAVE NO RIGHT TO JUDGE - which reran David's "My Mother Is Insane!" spoof.) I'm glad he's doing the "Bring Back Roomies!" as I never was able to get through that or "It's Walky!"
Others I would include are "Hijinks Ensue" and "Girls With Slingshots" which I follow on Comics Chameleon. I tried "Something Positive" but even though Mulholland's guest QC strips have been hilarious, I just can't get into the regular strip.