Not saying I necessarily subscribe to this theory (and I don't know if it's been posted on here before), but
www.laddertheory.com is definitely worth checking out. Mainly because there are some truths in there that I'd rather not admit to myself or anyone else, but I will say this- if a guy is awesome enough to be my friend, and I find him physically attractive, chances are I'll have a crush on him at some point. Although I do find guys exponentially more attractive based on how nice and/or funny they are, which this website says is all a lie. So I dunno, take it with a grain of salt I guess.