PhotoRec

PhotoRec is an open source multi-platform app intended to help you recover photos from corrupted media like memory cards and even hard drives and CD-ROMs. In addition to photos, PhotoRec can recover many other types of files, including video files, documents, and archives (e.g. zip files). PhotoRec ignores the filesystem and goes after the underlying data, so it'll work even if your media's filesystem is severely damaged, and it'll work on FAT, NTFS, or ext2/3 systems.