Today only, Newegg offers the Toshiba 500GB Serial ATA 6Gb/s 3.5" Internal Hard Drive, model no. DT01ACA050, for $54.99. Coupon code "GREENMD202" cuts it to $39.99 ($0.08/GB). With free shipping, that's $16 under our January mention and the lowest total price we could find by $12. It runs at 7200 rpm and features a 32MB cache.
Note: In order to redeem the rebate, you'll need to activate the Total Defense software, which involves providing your credit card information. However, you can cancel the service at any time within the first year without any additional charges.