(In order of recommending)
http://www.blastwavecomic.com/ - Funny comic about war, has great art.
http://www.amazingsuperpowers.com/ - Dark humor, anything seems to be fair game on this comic. Also, I found it through one of the comic's artists plugging it on a NG user post. I forget they're name tho. Keep your eye out for a clickable frame in each of the newer comics, they lead to 'secret' gag panels.
http://www.penny-arcade.com/comic/ - What can I say, they have their own expo, the comics good.
http://www.ctrlaltdel-online.com/comic.p hp - I used to be able to recomend this but as of late it's become incredibly formulaic, but who knows it might still have the occasional moment.
http://www.vgcats.com/comics/ - I actually like VG Cats more than CAD at this point, but VG Cats updates are really slow.
http://www.myextralife.com/ - Another decent gamer/pop culture comic
Apart from that, I'm not sure what else is out there in terms of worthwhile comics. Making a comic has been one of my goals for a while now, I've been exploring some designs for characters actually.
(Shameless Character Design Plug)