Bitlash is an open source interpreted language shell and embedded programming environment for the popular and useful Arduino.
The Bitlash interpreter runs entirely on the Arduino and interprets commands that you type in a terminal window or send programmatically to the serial port:
bitlash here! v2.0 (c) 2012 Bill Roy -type HELP- 942 bytes free
> print "Hello, world!", millis()
Hello, world! 11939
>