ProZ

ProZ is one of the largest online communities and job forums for freelance translators. It supports a very wide variety of language pairs, and while standard membership is free, a paid membership allows you to bid on more projects earlier. In addition to resources and articles on translation and finding work, the translator community forums are very active. ProZ also hosts periodic translation contests. While one can have a basic account for free, paid membership opens more job postings and allows you to bid on them earlier.