soz, now with the guidelines we've gotten from this discussion, I'd say Sheldon is the classic super-nerd, super-geek combo. Raj, Howard, and Leonard are pretty much nerd, with a little geekiness. Stuart the comic book store guy is pretty much pure geek, and Wil Wheaton is the Darth Vader of geekdom, which kinda makes him geek squared. Amy Farrah Fowler perhaps outdoes even Sheldon in nerdiness.
I'd suggest watching "Big Bang Theory" on Thursday nights for a crash course in geekery and nerditud (at least it's on Thurday nights once all the damned basketball gets done).
This show is so funny! Rock, paper....
ooooh yeah,....scissors, lizard, Spock, the ultimate nerdy difference-settling tool, good vid, t2l.
Nerd is usually an outsider, that dresses in a special way, and do things that isn't excatly considerd normal.
A geek can be a nerd, but also a normal person excelling at an area of expertize.