Babuino Project is the first application I know of the open-source Arduino as a programmable Robot plataform.
By programmable I mean the user can develop codes and download them to the board without the needs of a compiler. Babuino Project embedded software is a LOGO Language interpreter, so anyone who has an Arduino board can use some free LOGO softwares to program the board.
Here you'll find the history of this development, applications, tutorials, and LOGO programming examples.
I hope you enjoy Babuino Project.