The best internet based comic I have ever come across is Bob The Angry Flower. It's varyingly clever and nonsensical, but always terribly and cynically hilarious.

www.angryflower.com

My favorite is http://www.questionablecontent.net.

Only one I enjoy which has yet to be mentioned is http://www.sinfest.net

I check penny-arcade more frequently, but it can get a bit old... I enjoy sinfest's variety between the main characters, god and the devil, and the pets.

www.mnftiu.cc

My New Filing Technique Is Unstoppable and Get Your War On are both excellent. One day if you're bored and need something to do, just start at the beginning of filing techniques or GYWO and prepare to laugh. Filing techniques is basically a zany look at interoffice relationships. GYWO is a huge collection of current events inspired comics that began shortly after 9/11. Great stuff, unless you're a Dubbya fan.

It used to be decent, but it's more or less the same thing nowadays. It's either "LOL PINTSIZE IS A CRAZY ROBOT", "LOL INDIE GIRLS ARE HOT BUT SASSY," or "LOL MARTEN IS A VIRGIN" jokes. And nothing but.

Also, the art has been on a steady decline since halfway through last year. It's like he figures now that he's profiting off the comic, he doesn't have to try anymore.

I dunno, I still like questionable content. The others I peruse that were also mentioned include ctrl alt del (definitely my all time favourite), 8bit, and this other one that wasn't mentioned.

http://www.leasticoulddo.com/

Hilarious shit there, going through the archives it's had a few phases, different artists and such, but overall it's so friggin hilarious. Hell, I even went and bought the new comic book they are putting out.

On that note, actually, forgot to mention I also subscribe to the ctrl alt delete premium thingy, for the animation and special stuff. The animations are SOOOO worth it, hilarious stuff. Bit shorter than one would figure they need to be, but quite well done.