I wouldnt bother with refubished Hard Drives, as they have mechanical parts that actually show wear over a short time compared to silicon.
Check out www.newegg.com
for usually good prices.
In case you were wondering, make sure you get a hard drive that spins at 7200rpm, and has an 8MB cache.
It seems the most reliable hard drive brands are Western Digital and Seagate. I have used Maxtor, WD, and Seagate, and have no preference as of yet (except the Seagate has a better warrenty).