Ben Cheney is Angela's BF. He loves to watch ninja movies. It is suspected that he is bisexual. He is said to be rather short in comparison to Angela, and is also apparently Chinese, although his last name is not Chinese whatsoever. Unless, of course, Meyer is simply trafficking in the "AZN R SHORT" stereotype. We don't hear too much about him, probably because he is a) Not Bella b) He does not sparkle and c) He is not a pedophile.
In Midnight Sun we learn why he was created. He is a tool to show how kind and grateful Eddie is. After violating Angela's privacy several times (looking through her mind to stalk Bella) even while she was changing (proving what a peeper he is). He decides to thank her (or pay her, as you wish) and searches for something he can offer her. Conveniently the only thing (yes I mean thing) she wants is Ben Cheney and through acting in front of him as if he wanted to ask Angela out, he brings Ben to ask Angela out for prom. Eventually this happens not because Ben is hurt in his pride and wants to prove he's better than Edward (what Eddie was actually planing) but because he wants to protect her from the creepy Edward. While we can fully understand his feelings towards Edward it is quite chagrining that he thinks Angela is not able to protect herself and needs his manly power. Meyer being sexist again - not surprising anymore, just