Credit:
BooksOnCampus: A site that's now using the Facebook API to enable book swapping on college campuses. BooksOnCampus was founded in 2003, but the Facebook integration is brand new this week. Just as existing sites have rolled out MySpace widgets to extend their reach, it seems that the Facebook API has inspired a number of older sites to enable Facebook logins.
BottleTalk: A social network for wine lovers that launched officially last week. Includes tagging, profile pages, ratings, tags, search, a network of friends and RSS feeds. BottleTalk is based in the UK, has a few hundred members and seems to be off to a good start. The wine cataloging service Cork'd is doing a similar thing.