I have an arduino due on the way and was thinking, since it has more than enough io pins for an sd card, and maybe even external ram chips if needed, would it be possible to load a basic version of linux or something similar? Surely if possible it would require a custom bootloader that tells the processor to jump straight to the sdcard and start executing the system from there, just a thought I had
I don't think so.
Perhaps the wrong processor and not enough memory to run an (up-to-date) linux version.
http://arduino.cc/en/Main/arduinoBoardDue
Similar question here : Embedded Linux on Arduino DUE - Arduino Due - Arduino Forum
The Arduino Yun has a wifi/linux module that runs OpenWRT linux.