An overview of free/opensource software for data recovery:
Recuva for Windows, one of the most famous recovery software with many features
MiniTool Partition Recovery for Windows, supports many file systems and various kind of hard disks
Undelete Plus for Windows, it also recover images from CompactFlash, SmartMedia, MultiMedia and Secure Digital cards
PC Inspector for Windows, has also recovery feature of images, videos, documents, sounds, damaged archives)
TestDisk multi OS, supports Windows and Linux filesystems and partitions, repair boot sectors and has many other features!
Restoration for Windows, it also recover from digital camera cards, it’s standalone
R-Undelete e R-Linux for Windows e Linux; from same developer we find other recovery specific tools like R-Mail, R-Word, R-Excel
PhotoRec multi OS, it recovers files and photos, videos, documents, archives…
Pandora Recovery for Windows, it recovers many kind of files
CD Recovery Toolbox specific utility for CD, DVD, BluRay recovery
Zero Assumption Digital Image Recovery specific utility for images and videos recovery from digital cards
DiskDigger it also recover from USB flash and memory cards