I've had horrible experiences with Western Digital. In my experience, they're pretty unreliable. Lots of folks disagree with me, but Mrs. RC and I have had two crash on us.
Seagate has always done me right. All the Women's Studies footage and edits are backed up on them. They used to do a 500GB FireWire drive for under $100, but those seem to have gone the way of the dodo. Recently, I purchased a 1TB USB drive to back up all the Helena vids. That drive ran me $130 plus tax at Best Buy.
The key with externals is you want to move the data to a new external about every five years. Yes, trash the old one. If you're just archiving, you want to fire up the drive at least once a year to make sure the data is all there. Store in a cool, dry place and even get some of those packets of silica gel to absorb any moisture that may get in there.
But USB should be fine and easy. Most externals have backup software that installs automatically, but if you're just storing media, don't even bother with it. Just open up the drive on your desktop and start moving files. USB will take awhile if you're moving gigs and gigs of footage at a time, but just copy in batches and go grab a beer or read a book.
Hope this helps.