I sort of know how you feel, I've had girls that are friends of mine tell me that they like me or make it obvious, but I'm not attracted to them. It's a bitch of a situation.
If you're really not attracted to them, then don't go out with them. Don't think that you're obligated to complicate your relationship with a girl you don't want to get intimate with just because you're their friend or you don't want to hurt their feelings.
Explain to them that you'd rather stay friends than get into a relationship. There are a bunch of things you can say to help make it easier on them emotionally. You could tell them that you don't think you're ready for a relationship or you're just not looking for one, for example. Don't just come right out and tell them you don't find them attractive, that'll hurt their self-esteem.