LiveMocha is an excellent site to use to learn another language. You can also help others learn a language. This site combines the idea of an educational site with a social networking site. It uses audio and graphics, and the quiz model to help you learn.
The aspect that I like is the social networking component. Practice writing in that language and others will provide you useful comments.
LiveMocha provides some nice practice exercises for those studying for the TOEFL exam. Select English then TOEFL to view these lessons.
If you want to learn another language, practice for the TOEFL exam, help others, or want additional material for your students, check out LiveMocha.