Western Digital offers its factory-refurbished WD My Passport 500GB Hard Drive for Mac, model no. WDBL1D5000ABK-NESN, for $34.99 plus $5.99 for shipping. That's the lowest total price we could find for a refurb by $5. It works with Mac systems right out of the box and can be reformatted for Windows. Features include USB and compatibility with Apple Time Machine. A 6-month Western Digital warranty applies.