It’s the perfect nightmare and everyone do all his best to avoid it but sooner or later it happens.

Loosing data from a hard disk or a USB device is more common than you can image and everyone has experienced it!

Windows has different commercial solutions available to recover data and partitions but, if you use Linux, you need something different.

The best solution I found for Linux is an old but current article by Lifehacker.au that I strongly recommend if you are experiencing this kind of problems and want to solve them.

Recover Data Like A Forensics Expert Using An Ubuntu Live CD
Plenty of utilities can recover deleted files, but what if you can’t boot your computer, or the whole drive has been formatted? Here’s ho…
http://www.lifehacker.com.au

To sum-up the above mentioned post, you could need three different packages:
1 – testdisk;
2 – foremost;
3 – scalpel.
The use of each of them allows you to solve all – or specific- issues related to the data recovery you need.

Please, add a comment if you know other good tools for Linux on this specific topic.