This is a short directory of t-shirt and apparel sites:

 Split Reason - http://www.splitreason.com - T-shirts and Flexfit hats for geeks and generally smart people.

ThinkGeek - http://www.thinkgeek.com

Game-Skins - http://www.game-skins.com

T-Shirts.com - http://www.t-shirts.com

T-Shirt Hell - http://www.tshirthell.com

Error Wear - http://www.errorwear.com

HackerThreads - http://www.hackerthreads.com

JinxHackwear - http://www.jinxhackwear.com

Threadless.com - http://www.threadless.com

Jive T-shirts - http://www.jivetshirts.com

T-shirtsthatsuck.com - http://www.tshirtsthatsuck.com