Quizlet -??My Flashcard sets
nciku -??My vocab lists
Livemocha -??My profil
I also use ChinesePod audio podcast a lot but never been a paid user.
Language leaning should be this way build around a community of peer who help each other. After all when you learn a new language isn't it because you want to increase the range of people you can communicate with?
Learning the language should naturally integrate the possibility to make new friends you can practice with immediately.
It should also be open by default. If you create flashcards, vocab lists… share it with the community. If you dont want to and you used a lot of ressource, then you should pay for it.