Hi this one is fairly easy to use http://www.arduino.cc/
like you said. I have not used it though but I have worked on many of the Atmel MCU's and motorola MCUs. Once you get a kit its all very easy. My advice is that buy a STK500 and a dragon(burner cum debugger) from the atmel's website and get going. Also let me know if I could be of any help to you.
PS- Motorola has a disadvantage that its MCU's doesn't have much support available on the internet so you will have to screw your own head even for the minimal amount of work.