I was beginning to wonder if anyone would mention dorks. Geeks, nerds, and jocks have all been accounted for, but what about the dorks? To elaborate: nerds are the smart type who use their smarts to make money and/or make the world a better place; geeks are your comic book collectors, star wars maniacs, trekkies(basically sci-fi freaks), ren fair attendees, Harry Potter freaks, band geeks, Dungeons and Dragons players, Magic: The Gathering players, anime/manga fans, etc.; dorks are the social outcasts who fit into neither the "nerd" nor the "geek" category; and jocks are the fit, athletic, sport playing types.
If you are still having trouble, here's some Simpson's references that should clear things up:
Martin is a nerd:
Comic Book Guy is a geek:
Milhouse is a dork:
I don't know of any jock characters from The Simpsons, so here's a jockish picture of Bart:
I hope this clears things up for you.