Following my post I got tipped off to this drive for MacBooks. Basically it is a converter for a microSD card, but specially designed to fit in the SD card slot of a MacBook without protruding. That alone is pretty neat, but why would you want this?
Well they actually did a pretty good job of persuading me to get one: use it as an integrated backup drive. They note you can only get a 64GB microSD card right now, but that the Nifty MiniDrive supports up to 2TB — which would be slick.
Anyways, I backed the project and look forward to putting my SD card slot to a lot more use. I plan on using the drive as my Aperture ‘vault’ location for backups.