JWTWEAK  I had a media card (SxS 16 GB) full of HD video (indie film) go bad on me yesterday. Couldn't see data or even reliably mount the card. Needless to say, this was not a good thing. Spent hours trying everything I could think of, with various well-known software packages, trying to get anything recovered. Even spent money on some other media card recovery software in desperation. Nothing worked in any way. Until I tried TestDisk! WOW. Sure, it is a command-line program, but IT WORKS and it COPIED the data INTACT without much trouble. I'm near ecstatic. THANK YOU, TestDisk!  
(Version 6.10)

BCWINTERS  Saved my external firewire drive that had been incorrectly ejected (and had a damaged partition table as a result). DiskWarrior couldn't do it; Drive Genius couldn't do it; TechTool couldn't do it...yet tiny open source freeware TestDisk (along with companion command line utility pdisk) salvaged the partitions in a matter of maybe four minutes.

The documentation (like that of so many open source projects) is a bit arcane, and those of you who are not comfortable in the Terminal might be a little nervous about this app. But I found a walkthrough that made it dead simple.

This is a brilliant little utility that's going right into my recovery arsenal.  
(Version 6.10)

WAKAYAMA  Brilliant, brilliant app! Having accidentally destroyed the master boot record (MPR), and lost a couple of partitions on my macbook pro internal drive, AND gone through the usual suspects for trying to resurrect a drive, I was beginning to despair and just on the verge of shelling out $100+ for a programme to just get the files back (but wouldn't resurrect the partition itself), I came across this little app.

The destruction manual could do with a little more info, as I didn't really believe it could do the job all by itself from what I had read, but lo and behold, it did. For free, as in beer.

If you are trying to recover a lost partition, give this a shot - especially on an intel mac, it's suhweet.

Cheers to the developer(s) for this!

(I tried to enter this as a review, but macupdate isn't loving me today. So here are my five stars *****)  
(Version 6.10)

TSEHOV  This is one of the greatest free apps I've ever used. I have solved some very difficult problems concerning data loss a couple times both in Windows and Mac.

This is very capable software even when compared to those expensive apps.

Many thanks for Christophe Grenier making TestDisk and giving it free to everyone who needs it.  
(Version 6.10)

ROBK  After using TestDisk, you don't need to use gpt to recover the newer EFI partitions used on the Mac. TestDisk can recover damaged or accidentally deleted EFI partitions used on the Intel Macs all by itself!

Just use TestDisk to identify and repair EFI partitions on Intel Macs. It is very simple.

You only need to use the Apple pdisk command to restore damaged or accidentally deleted Apple partitions used on the older PowerPC Macs. TestDisk will not restore Apple partitions used on PowerPC Macs.  
(Version 6.9)

JOHN SAWYER CJS  Maybe it's called PhotoRec to get the attention of people who have problems with their camera memory sticks, who might not have realized they might be able to use it to recover their photos, if it had some generic name.  
(Version 6.9)

ROBK  Finally some FREE GPL'd data recovery software for the Mac. For those who dpn't want to pay $99 or more for data recovery software, TestDisk and PhotpRec may be the ticket!

But why is the second program called "PhotoRec"? The name is misleading. Not only can PhotoRec be used to recover Photos but it can be used to recover many other types of files like documents and archives.   
(Version 6.9)