PhotoRec saved my ass just earlier this week, after an accidental wipe of a CompactFlash card with client photos on it.

As another commenter noted, create an exact dupe/image of the volume as the very first thing you do.

Also: if it doesn't successfully retrieve files on the first go, try another configuration. I think it took me 3 attempts to get it right.

A fun perk, also noted in the article: you may get back some surprises along with the files you expect - older files revealed in the sediment!