This isn't a hard drive per se, but it allows you to hook your PCs hard drive up to your 360 and shuttle data back and forth with reckless and hacker-like abandon. Plus it has blue LEDs, which means it's good.
The XSATA attaches to your XBox hard drive and turns it into a USB drive. You can then drag and drop content and even grab and email saved games. Not way to hack Live content likes games and things, but that shouldn't be far off, right?