Today Raspberry Pi, the awesome $35 Linux computer and Wolfram Research announced a partnership to offer Mathematics and The Wolfram Language on the Raspberry Pi for free. Future releases of Rasbian, the defacto OS for the Pi will include it preinstalled.
If you need a Raspberry Pi, even Amazon has them.
To get it on your Pi today, just open up a terminal window and do:
sudo apt-get update && sudo apt-get install wolfram-engine