Quick post, to present a project to connect a Arduino to a Linux embedded system thought an I2C bus.
For the project I used a NGW100 (AVR32 processor), but you can do the same stuff on all Linux embedded system that has a I2C bus, for example a Fonera or WRT54GL.
As you can see on this pix, only 3 wires are needed (SDA/SCL/GND) :
Please note, that I used a seeeduino board because it can work at 3.3v or 5v, and for this kind of stuff 3.3v is usually needed.
All informations are here : Connect NGW100 Linux (AVR32) to Arduino with I2C | Jkx@home
Feel free to ask question, hope this help some Linux embedded enthousiasts