How to recover data from a damaged SD card?
I encountered the same problem with my SD card and Samsung Galaxy S a while ago. The solution was to plug the card into a card reader and run chkdsk x: /F /V to repair the file system. 

If this doesn't work, you'd have to use some file recovery software to fish out the files from a broken file system. There are many different applications for this, you can find some by googling for "file recovery free", or try PhotoRec.