Check TigerDirect and Frys often. The Seagate Portable 2TB was $80 recently. I think yesterday.
Also if you have Win7 or Win8. It has a built in imaging tool. On Win8 you'll see buried in the Control Panel's File History.
However, if you are interested in backing up your files and profile, then Windows Easy Transfer has surprised me. It's available on Win7 from the start menu, but it's again, BURIED in Win8. On Win8 you'll need to dig into the installation DVD's support\migwiz folder. If you have the Win8.1 DVD, it's not there at all, but luckily the Win8 version works just fine.
Like everyone mentioned, backing up to the cloud will take forever for most Americans. Our Internet speeds are embarrassing compared to the rest of the world. To make matters worse, our upload speed is what'll hold you back. If you're lucky you'll be getting .5MB per second upload. I wish that was a typo.