I use a Western Digital My Book Home Edition 500gb for my media, backups, and schoolwork
It is very fast and quiet, but there are two small annoyances with it-it makes a buzz when powering up and after it is in use for a few hours running iTunes music, the songs will occasionally skip (about once every 15 minutes after 4-5 hours of trouble free use)
I got it for about $120 at Costco and partitioned it into a Movies, Photos, iTunes, Backup, and Other partitions using Disk Utility
It comes formatted to Fat32 so you must first copy the included folder off the drive, then format it with Disk Utility
The included software in the folder on the disk just tells the drive how to light up.