These are the biggest question I have before I will start to use AVR, which OS's can AVR interface with, how do you get AVR to work with the gumstix setup, what compilers would you use once it's interfaced with the gumstix, and which compilers are good? I might get the arduino board to try out, a lot of people say the C compiler is great and works on all platforms, which is what I like, because I can use Mac OS X for AVR. But I want opinion's of other people's experiencing and some recommendations. Thank you.

I use AVR-GCC C compiler. It is free and works on Linux so I would imagine you could get it for a Mac. Just google "avr gcc mac". I really like it and have had no major problems except when I tried to convert a string into a float. The library for Ubuntu 8.04 did not work and made the AVR reset. I was told this only happens with Ubuntu 8.04. I simply wrote a small function to do the same thing. It might even be fixed by now, that was a while ago.

To program the AVR I use AVR Dude and the AVR ISP 2 programmer.

Justin