If you need a portable USB hard drive for backup or storage purposes, Staples has a nice Simpletech 500 GB drive for only $69.99.  It is the Signature Mini Expresso (black) drive with a velvety soft-touch surface that is easy to hold onto.  I have the Marshmallow (white) version of this drive and it has served me well.  Because it is a small portable drive, it needs no external power source.  It will run on the power supplied by most USB ports.  A USB cable is included.  This is a web only special, but it qualifies for free delivery.