External hard drives?

Appealing to my flist for information here :)

I know next to nothing about computers. I would like to get an external hard drive or a zip drive or something that I can back up my files with. I would be backing up word docs, photos and a bunch of .avi files (tv shows and movies). Anyone have any suggestions as to what device would work best for this? Any info- like what brands are good or which ones should be avoided or what storage size is ideal would be appreciated.