I'm not sure how I feel about buying a "recertified" hard drive, but I do know I like the value proposition in picking up a 1TB WD Caviar GP for $129.99. That's a nice discount off of the terabyte Caviar GP, which is already the lowest-priced terabyte drive on Newegg at $159.99.
Despite the spindle speed weirdness involved with the GreenPower scheme, we found the Caviar GP to be a decent performer with very low noise levels, though it's not the fastest thing around.
If you're willing to live with a little more potential risk, the recertified one looks like pretty good deal. When coupled with an external enclosure, it might be a nice solution to your backup dilemma. Thanks to cobalt for pointing it out.