I've had good luck with a Seagate FreeAgent and Iomego eGo BlackBelt (cute name, but tough as nails).
Use to back up with DVD's but so much easier with a USB external.
At the current prices buying two is really not that much and gives double the protection to valuable data. Valuable is relative, but to me its any file(s) that I really need or have put a lot of time into.
Unless your have a huge amount of data or are storing multiple full backups or drive images, you can likely get buy with 500GB nicely. My Iomega is 500GB and has a dozen sequential full copies of my data files with room to spare.
Personally, I'd wouldn't use the backup software they usually come with. Then you don't need to find that software to get to your files.
IMHO, its too much trouble for specific file recovery and in all my years I've only done one full restore of a system, and that was with a drive image program (like Acronis TrueImage or Norton Ghost) from my network server to the desktop machine I'd trashed.
I always doubted the likelihood of a full restore from basic backup software actually working.
For that matter I usually avoid their install programs. Just plug it into the USB port and use it like any other drive.
I use SyncToy to copy files, which is fairly simple and free from Microsoft. Once set up, a couple of clicks and all the folders you have specified are copied.