Wolfgang's Vault is an online warehouse of tees that were actually created for and sold at rock concerts from the 1960s through today.
A quick scan of this Web site brings you back to your college days - or at least the halcyon days you wish you'd experienced.
If Cream or the Grateful Dead are your thing, or if you are more into U2 and Nirvana, you can find a shirt on this site. And they are way cool! Sure, they probably smell a little musty and are pretty creased from being boxed up for 30 years. But, hey! That's precisely what "vintage" means, and that's exactly what keeps you out of the "poser" category.
The site also sells tees and posters that are newly made but replicate the vintage artwork; it calls this category "retro." The posters range from rock shows and stand-up comedy nights to art exhibits and films.