Ran acrossed this little video
Here's the web page with more detailed instructions:
I might actually have to do this!
If you like that, you may be interested in an Open Pandora. http://openpandora.org/
It's a mini Linux device with a full qwerty keyboard. There's so much you can do with it but I only used for emulation though- before I sold it it featured a DS emulator and someone was working on a PSP emulator. The community is great too.