SpinRite, from GRC, is a very low-level hard drive maintenance and recovery tool. It isn't free ($89 for first-time purchases), and it is not terribly pretty, but is very advanced. The UI (and their website) needs some design help, but they have the tech side of things down.
DFSee (€49) is not for the neophyte but looks comprehensive (i've never used it). DFSee is a generic disk, partition and filesystem utility for maintenance and data-recovery.
Hard Drive Mechanic is another commercial, but slightly less-expensive ($69), product option.
Other choices include SeaTools from Seagate and Western Digital's Data Lifeguard.