For some odd reason it seems that custom designed tees are all the rage wth the hip young kids these days. gothamist.com is pushing TinyFactory, who also happens to be publishing the gothamist.com t-shirt. Cafepress is old news, so I'll skip the link (plus, rumor has it they have quality problems). And monkeyfilter.com is having a t-shirt run custom made for their members (I bought one). I stumbled over Stepinrazor's comments in a thread, and found this particular outfit called threadless that's taken this to a new level (of INSANITY). Instead of just making tees, they have contests and people rate the tees. Whatever hip design gets populor, they print a limited run and sell. Most of the designs are these too-hip artsy designs that look pretty good (to a hipster) on the screen, but I don't think anybody would be caught dead actually wearing in public. Or at least, I haven't seen one yet. But there are a few gems in there. You just have to do a little digging.
Link: