From the Toys section:
Amazon.com offers the Hammer MoreSpace 500GB 2.5" USB 2.0 Portable External Hard Drive, model no. HP1100-500, (pictured) for $78.83 with free shipping ($0.16/GB). That's the lowest total price we could find by $26. It's also one the least expensive 500GB portable hard drive we've ever seen. Note: You can take out the 500GB SATA drive inside and install it into your MacBook/Pro.
