Second Life (secondlife.com)

Second Life is a popular virtual 3D online world that wasn't specifically created for the purposes of learning languages; however, the potential for applying it to language-learning is enormous.

Basic membership to Second Life is free, and you can join language-specific communities, such as ones in Spanish, Dutch, Brazilian Portuguese and Swedish.

This virtual online experience, while primarily in English, allows you to interact in these (and eventually other) target languages, and it's easy to find community events where you can meet other avatars.