Buy.com has the Seagate 500GB Free Agent External Hard Drive, now priced at $104.99. Shipping is free and there is no sales tax (except CA, MA, MD, TN). Seagate is the premier brand when it comes to external storage, and $0.21 per gigabyte is a great price. It's compatible with both PC and Mac and comes with the five-year warranty. Plus, new Google Checkout users can get a $10 off discount for signing up and new Buy.com customers can activate this $5 off $100 (you can't use both).