PhotoRec is a great bit of open-source data recovery software. It’s cross-platform and runs on Windows, Mac and Linux. It’ll recover lost files including photos, video, documents and archives from just about any media. It ignores the filesystem and goes straight to the underlying data, so will still work on cards that have been severely damaged or reformatted. It won’t attempt to write to the media you’re trying to recover from, so is safe to use. It also has a great companion program, TestDisk, whose job is to recover lost partitions as well as making non-booting disks bootable again.