Check out Fair Wear! The graphics are designed by mcmillan who draws minimumsecurity. The T-shirts are made in a factory in Bangladesh that strives to pay it's workers a fair, living wage, and 1/3 of the cost of what you buy is returned right back to the workers in the factory where it is made. That means for an $18 dollar shirt, $6 goes right back to the workers!
I'm going to buy a treehugger shirt in plum, as soon as I know I can afford it. That's Kranti, the star of minimumsecurity. :]