Recovering data is no small deal -- as anyone who's lost some will attest. But with so many programs out there, it's had to choose. The latest version 7 of O&O's DiskRecovery ($100. feature-limited demo) is making a strong argument to be your first choice, although at $100 is pricing itself beyond trusted veteran software such as R-Studio Data Recovery and Active@ File Recovery.
DiskRecovery 7 is actually three programs in one: a simple file un-deleter, a sector-based scanner, and a sector-based scanner that can operate on damaged file systems and disks. Sector-based means the program follows the links between data sectors rather than the map provided by the operating system. You can choose to use one, two, or all three of the methods for any operation.
In my tests combining all three methodologies, DiskRecovery 7 found tons of deleted files...however, much of it was useless Windows temp files. I highly recommend that you limit the types of files it searches for using the file types tab in the Adapt (additional settings) dialog when doing a deep scan. Doing this made for a much shorter and cleaner list of recoverable files.
O&O DiskRecovery 7 is easy to use, and it walks you through the recovery process step by step. The approach strikes a nice balance between utility and usability -- an amateur can get the job done, but a pro won't think it underpowered. Like some of its better competition, DiskRecovery 7 allows you to save the results of a scan for later analysis and recovery. It also works on images of disks created by O&O DiskImage.
One useful thing DiskRecovery 7 doesn't provide is an emergency boot disc. However, you can create a portable installation on a thumb drive and run it on the afflicted computer. If the operating system on the disk containing data to be recovered won't boot, you'll need to attach the drive to another computer -- my preferred method in any case.
O&O DiskRecovery worked perfectly for me, but I haven't used it nearly as much as the aforementioned competitors. Still, if your drive is not in imminent danger of dying, give the demo a shot. It will show you what it can recover. The demo won't save recovered files, but if it finds more files than others (and it includes the ones you want), buy it.