I have just returned to using AVR chips, in particular the ATtiny2313 and it really is tiny to use. I am running on mac os x, and avrstudio wont run on mac, but luckily there is an eclipse avr plugin that works really well. First of all you need to install an avr compiler, avrdude. You can find it to download here cross pack. This provides you with a command line compiler for a selection of avr chips.