NOTE: you can find the newest version at: http://blog.windfluechter.net/content/blog/2011/03/30/1095-updated-automatically-restore-files-lostfound
Ok, my last version was a pure Bash solution: working, but slow. There were some comments how to improve the performance and I decided finally to reimplement the second script as Python script.
The Bash script didn't finish within a day. The Python script ends after 1-2 hours in my test scenario. So, here are the scripts again:
make-lsLR.sh - call this regularly (cron) to create the needed files that are stored in /root/. Of course you can alter the location easily and exclude other directories from being scanned.
check_lost+found.py - The second script is to be run when your fsck managed to mess up with your files and stored them into lost+found directory. It takes 3 arguments: 1) the source directory where your messed up lost+found directory is, 2) the target directory to which the data will be saved and 3) a switch to actually make it happen instead of a dry-run.
I've chosen to copy the files to a different place instead of moving them within the same filesystem to their original place for safety reasons. Primary goal is to retrieve the files from lost+found, not to replace a full featured backup and restore application. Because of this the script doesn't handle hard- nor symlinks correctly. It just copy files. Of course there's still room for improvements, like handling hard-/symlinks correctly or using inode number instead of md5sums to move data back to its prior location. But it works for me[tm] well enough in this way, so I'm satisfied so far. You're welcome, though, to improve this piece of ugliness if you like. Maybe someone else finds this usefull as well. Use it on your own risk, of course. :)