Social networking sites like MySpace, Facebook, and Twitter are more general, these few websites are based on common interests:
this site is especially for booklovers. Once registered you can create your own bookshelf, take a peek at what other people have on their bookshevles, and also write comments about the books
this site is for people interested in learning a foreign language. you can choose to teach or to learn and connect with people who are also trying to learn a different language
from their website: CouchSurfing seeks to internationally network people and places, create educational exchanges, raise collective consciousness, spread tolerance and facilitate cultural understanding.