I like newegg.com and ncix.com for online parts. If you are just using the drive as storage than save some money and a bit of power at the same time with a "green" drive. Just make sure you have an adequate backup solution in place. I think you can get the 2TB green drives for about $100. NCIX has a price matching feature during checkout so use your price comparison websites once you have selected a drive.
edit: that deal above is not a good one, you should be looking for at least 1.5-2TB for $100-$120 price range.