Cr0sh, well it is some time since i used stamps, i know they have come a long way now, but the way they used to work was the PIC ran a basic interpreter on chip and code was stored in an external eeprom, programming was done through rs232 terminal, there was no external compiler, theres no reason why an arduino could not do the same although, it would slow things down alot having to read/write to an external eeprom, as was with the basic stamp, slow.