If you need to recover files and/or partitions on Linux, TestDisk and PhotoRec may be useful. Both are very powerful and free tools that run on Linux and may also work if you need to recover data from USB Hard Drives, USB Memory Drives, Memory Cards, CD-ROMS, iPod, etc.
Despite its name “PhotoRec”, this tool can also recover many other file formats that are not specifically media (images, video, sound) files. It works a bit differently from some other (free) recovery tools in that it ignores the file system and scans the underlying data directly by attempting to recognize patterns in the data itself. One drawback is that because it ignores the file system, it will generate arbitrary names for the recovered files (file names are normally stored in the file system itself). That means that if you have to recover many files, it can become quite the puzzle work to recover the original directory and name structure of these files; you would have to look at each recovered file individually. To recover just a few files, this should not be a problem, though.
However, some media files contain meta data including the original name and sometimes the timestamp of the file. Using some scripting and the ExifTool you may be able to extract that information from the media files and rename them back to their original name.