This looks interesting.
A program that cleans up all the un-needed files on your iPod, iPhone and frees up space.
PhoneClean is the first iPhone, iPad, iPod touch maintenance tool made to free up space and keep iOS devices running fast. This free tool will safely find and remove all kinds of iOS system junk files to cleanup and speedup your idevices, even no jailbreak is required. PhoneClean quickly finds and removes hidden temp files, cleanup corrupt media files produced by iTunes failed syncs, delete cookies and script files on your iPhone before backing it up to iTunes or iCloud to prevent the leak or the abuse of your personal information, deletes cache and offline files in order to keep your iPhone, iPad, iPod touch running fast and safe.
There's a video that shows how it works -
Get it here - http://www.imobie.com/phoneclean/
Edit, I just ran it and freed over 600MB on my iPod Touch :)