There's a $12 version on Kickstarter now: http://www.kickstarter.com/projects/443556734/pio-microsd-ad...
Adafruit will also offer a similar one soon: http://www.adafruit.com/products/966
http://www.kickstarter.com/projects/1342319572/the-nifty-min...
"An easy to use device that allows anyone to quickly and simply increase the available memory in their MacBook computer."
"NOTE: A couple of people have pointed out to us that we have mixed our terms a little. To clarify; when we refer to the MiniDrive increasing the "memory" of your computer, we mean the storage space, not RAM. Sorry for any confusion that this might have caused!"
edit: link and quote