BookCrossing Core - Create own BookCrossing site based on Drupal CMS.
Overnight - Book a last minute room with locals, in seconds.
BookMooch - BookMooch is a community for exchanging used books.
Airbnb - Book unique places to stay and things to do.
swap-bot - Swap-bot is a online service that organizes group swaps and a community of creative individuals.
FriendsTonight - Meet new friends to join your friends, tonight