Cyanide and Happiness
http://www.explosm.net/comics/
http://www.explosm.net/db/files/Comics/Rob/holidays.png
Just f---ing awesome. To quote <link=http://tvtropes.org/pmwiki/pmwiki.php/Main/CyanideAndHappiness>TvTropes quoting Wikipedia:
"Frequent topics of humor include disabilities, rape, cancer, murder, suicide, necrophilia, pedophilia, sexual deviancy, sexually transmitted diseases, self-mutilation, nihilism, and violence."
it may sound offensive... and it is! this is one of the funniest places i've ever seen, and you'd be an idiot not to check it out!
Saturday Morning Breakfast Cereal
http://www.smbc-comics.com/
<spoiler=a random example>http://www.smbc-comics.com/comics/20090624.gif
I just found it a day or 2 ago, and love it!
the humor is similar to XKCD in some ways, but the nerdiness is more toned down and understandable
XKCD
http://www.XKCD.com/
http://imgs.xkcd.com/comics/interdisciplinary.png
really funny, tho very nerdy humor, with a lot stuff like mathbased jokes
.
HONORABLE MENTIONS:
Order of the Stick
http://www.giantitp.com/comics/oots0001.html
(this is under honorable mentions simply because it is about characters in a roleplaying game rather than being stand-alone comic strips)
http://www.giantitp.com/comics/images/oots0001.gif
Antics
http://www.anticscomic.com/
http://www.anticscomic.com/comics/2010-06-25.jpg
The System
http://www.notquitewrong.com/rosscottinc/
http://www.notquitewrong.com/rosscottinc/comics/2008-07-03.gif