Lost some photos or trashed a hard drive? Have I got some fantastic (free) tools for you!

Both come from CGSecurity and both run under Windows, Mac and Linux (along with DOS, BSD, Solaris and more).

PhotoRec recovers lost files from hard disks and CD-ROMs along with lost pictures from digital camera memory cards -- hence its name. It ignores the filing system and goes after the underlying data instead, so it'll still work if your media has been severely damaged or even reformatted. It can recover lost files from FAT, NTFS, EXT2/EXT3 filesystem and HFS+ partitions.

Its companion program, TestDisk, recovers lost partitions on a huge variety of filing systems -- everything from BeFS to XFS -- and makes non-bootable disks bootable again. There's a step-by-step guide to running it here.

Both programs are open source software and licensed under the the GNU General Public License (GPL). Keep 'em in your toolkit!