How can I recover files from an iPod classic (when using as a hard disk) after reformatting?
If you are comfortable with the command line, try TestDisk

It's fairly intuitive for a command line program.

The basic steps are as follows:


Download from above link.
Extract download.
Navigate to extracted folder in Terminal.
Run ./testdisk
Follow the onscreen instructions.


Note: You may want to read the documentation before you do anything. The documentation links are about halfway down the page I linked previously. The instructions are for NTFS, but I imagine it will be a similar process for HFS.