Language learning is such a VAST and ignored area in start-up community. I'm also learning French and while Rosseta Stone is the mainstream software it's practically a wasteland with small occasional gems like http://babbel.com ( which is very nice Adobe Flex application). Anyone finding a quick and a fun way to learn a language will become an instant billionaire :) But I guess it's the general problem of knowledge learning and is as old as the human race exist. Imagine building something that has a possibility of destroying the current concept of school! For now all we have is sci-fi stories about swallowing pills for instant learning ....

P.S. I wrote a little Adobe Air application for someone who likes to learn a language while listening to songs or watching youtube. You can search lyrics/save/translate and bookmark your videos. It's a just organizes the whole process. Have fun ! http://www.singandstudy.com