MjM Photo Recovery provides a simple way to recover digital photos from memory cards, whether they've been accidentally deleted, or lost when the card was formatted.
The program is a little short on features. It can only undelete JPG images, for instance, and doesn't work with hard drives (it's strictly for portable storage only, memory cards and USB flash drives).
This does make Photo Recovery refreshingly simple to use, though. Just run the program, choose a device, click Search, and it'll immediately start scanning for lost photos. This can take a long time - several hours if you've a large memory card, perhaps 16 or 32GB - but the program does keep you informed by displaying thumbnails of the images it's located. You can view these full-screen, then recover all the photos or just the ones you need.