Everyone has a crafty friend who's great at something, so why not take advantage of her prowess and turn it into a crafty girl's night in? Whoever knows the most about the craft du jour comes prepared to teach the group how to do it.
Scrap booking, knitting and candle making are all great ideas that can be accomplished in an evening. Just be sure to plan ahead and send out a supply list. Craft supplies can get expensive, so ask friends to bring any surplus supplies that they aren't using. Ideally, everyone will leave with a finished project, or at least a good start on one.