Great Cow BASIC is a set of open source BASIC programming tools for Microchip PIC and Atmel AVR microcontrollers:
Great Cow BASIC has been written with three main aims – to remove the need for repetitive assembly commands, to produce efficient code, and to make it easy to take code written for one chip and run it on another. It hides many of the more confusing parts of microcontroller programming, making it suitable for beginners and those who don’t like assembly.
Thanks Sleepwalker3! Via the forum.