CloneZilla (older version for XP & earlier machines, newest version for Vista and up plus Linux and other variants)
Acronis (whatever the latest version is)
SpinRite (although I actually believe it's "snake-oil", I've personally seen too many instances where it actually worked)
UBCD (various versions)
Ubuntu on a USB stick (whatever the latest version is)
Pride-and-Joy = Homebuilt IDE->IDE drive copier (works with SATA adapters and newer 4K block drives as well), slow, not pretty, but doesn't require any operating system or any user input other than plugging it in, turning it on, and pressing the start button. Programmed it also to handle "bad" sectors by reading and re-reading the "bad" sector continuously until I get a 99% confidence factor on every bit in the sector (eg. 99 reads out of 100 are the same). As long as the drive is physically able to read sectors, I'll can get data out of it. It's brought back some pretty bad ones from the grave more than once.
...a handful of others...