Computers

Jinx Clothing Company
Online store selling many items aimed at gamers and geeks.
http://www.jinx.com/

Load Rage
Retro gaming designs.
http://www.loadrage.com/

NTKmart
Anarchic geek designs for those that Need To Know. UK-based.
http://www.ntkmart.co.uk/

OffLine
Featuring MMORPG, computer lifestyle, and fantasy shirts.
http://www.offlinetshirts.com/

ShirtMonger.com
Linux and classic video game designs.
http://www.shirtmonger.com

SplitReason.com!
Gamer and gamer logo products, t-shirts, Stikfas and Super Mario toys.
http://www.splitreason.com/

SysWear
Humorous computer-oriented t-shirts.
http://www.syswear.com