I'm surprised that Czech hasn't been mantioned here. I'd like to share some links that may be usefull for Czech learners and will be happy if you could add more
The Little Czech Primer - a small dictionary to begin with, samples of pronounciation are available.
Sklonovani - application conjugates the verbs (I don't use it myself as I think it spoils the learners).
http://www.factumcz.cz/K.Tahal-Grammar.pdf - a grammar of Czech as a foreign language.
Case Book for Czech - Exercises - the case book for Czech. Interactive exercises.
Radio Prague - No tip-toeing around the issue - Czech expressions through song lyrics.