It's taken some time, but magnetic hard drives are starting to feel the squeeze from their flash-based successors. However, until they're priced the same per gigabyte, the bulk of your data will remain stored on ever-more dense rotating platters. If you're in the market to expand your PC's storage space, it's hard to beat this deal for a 2TB USB 3.0 drive for $79.
Dick Smith is the provider in this case, though you'll need to punch in the following code to get the aforementioned price (it's $99 normally):
Note the $79 includes delivery, so no hidden expense there.
While you can use it as a backup HDD, there's nothing stopping you from cracking it open and putting it inside a machine. The hardware is reportedly a 7200rpm Barracuda with a 64MB cache, a great deal for $80.