If you are a geek to any degree, you will grin ear-to-ear browsing through this site. The designers of these products go beyond mere stereotypes, having creatively come up with stuff that embodies the essences of true geek cultures. Some of my favorites:
http://www.thinkgeek.com/tshirts/generic/724a/ : The geek love poem. For the non-geeks, #FF0000 and #0000FF are red and blue in hex color code, and All Your Base Are Belong To Us is a well-known geek meme.
http://www.thinkgeek.com/apparel/hats-ties/9352/ : Now if only I had an 8-bit suit to go with it.
http://www.thinkgeek.com/tshirts/generic/5d6a/ : 127.0.0.1 is the IP address that represents the universal home, or local host, address
http://www.thinkgeek.com/tshirts/illuminated/8e31/ : Hey, nobody seems to be winning.
http://www.thinkgeek.com/tshirts/popculture/78c6/ : Scaryyyyyy!
http://www.thinkgeek.com/gadgets/watches/6a17/ : On the bright side, it's far more robust than your regular LCD watch.
http://www.thinkgeek.com/tshirts/sciencemath/8953/ : Not quite the popular definition of heavy metal, but technically quite accurate
If you haven't had your fill of geekiness, here's a little bonus: http://www.ducttapefashion.com/