I really like the idea of Facebook friends but I think that a lot of people are using facebook with their real friends only so I have something else to suggest. I read an article about Tamdem e-mail projects. It means that students will write emails to other students using their first and second language. Then, when they receive the email of the other person, they corect the mistakes in his L1 (which will be the other's L2). You get the point? It is a good project for cultural awareness, ICTs, and practice of the language in real situations.
If you are interested to read the article here is the information : Dodd, C. (2001) Working in tandem: An Anglo-French project. In M. Byram, A. Nichols, & D. Stevens (Eds.), Developing intercultural competence in practice (pp.162-175). Clevedon, UK: Multilingual Matters Ltd.