I accidentally initialized a camcorder memory card with a friend’s movies!  Instead of being a schlumpf, I did the responsible thing and downloaded a program to resuce the data.  The one I found that seems to work for my Canon camcorder, which uses .mts files in my case, is called CardRescue.  Go here to download the software: http://www.cardrescue.com/ondownload.asp

It’s $40