Calvin and Hobbes - Official website. Each day it reissues an original Calvin and Hobbes strip 11 years after it was first published. Also has related e-postcards and merchandise.
Dilbert - How do people start the day without reading this? Funny nerd humor. Too much of the time this reads like someone's been spying on my office.
General Protection Fault comic - Daily comic strip about a software development company. Skip this if you don't get Dilbert.
PC And Pixel - A comic that can only be fully appreciated if you're a geek. Sort of twisted way to look at the world. Kinda like Far Side if written from a geek viewpoint.
User Friendly the Comic Strip - Very funny (nerd humor) comic strip about an internet company. If you don't get Dilbert, you might as well not bother.
