Seagate Barracuda ST1000DM003 1TB 7200RPM Internal Hard Drive for $49.99 after code this $20 rebate.  Shipping is $4.30 for a total of $54.29 shipped.  Here is a screenshot before the $20 rebate for your reference.  It features 7200 RPM, 64MB cache, and SATA 6Gb/s interface.  Most places have it for about $69.