Total Geek Lady here - I was a geek before it was popular.
Men with intelligence are a turn on. Inga from 'Young Frankenstein' was the first of us to admit it. We were turned off by rude jocks, abused for art by emo-goth boys, and ignored by all the rest.
The geek boys were sweet and treated us as people, even when they were shy. They willingly shared their world with us and encouraged us to participate in it. We weren't expected to be superficial with them, they wanted to see what our minds could create.
The raw exposure of one's mind, when we're surrounded by messages telling us to focus on appearance and facades and pointless drivel, is where the arousal comes from. It's more intimate than feeling up a jock's muscles because minds can connect on a deeper, more intwined level. Creativity is encouraged and used, and participation in the creative process is mandatory. Quiet studiousness also means he'll focus on you and attempt to unwind all your secrets and learn what makes you tick. He also respects you, and doesn't see you as 'just a pussy' or 'show off doll'; and usually doesn't care if you have some extra pounds. Although, libido-wise, they come in two flavors - dead fish or raring to go.
I love 'em.