A few notes on AVR microcontrollers, from Massimo Banzi:

About AVR...You can program them in gcc and this gives you a lot of mileage expecially because it runs on mac windows linux... and whatever other operating system

if you hate c, BASCOM AVR basic compiler is quite good and costs EUR 79 for windows

AVR processors can be programmed by any PC using the parallel port and 3 resistors... no need to build a fancy programmer for more serious stuff you should buy the STK500 for about 120 Dollars that allows you to program all the parts between 8 to 40 pins

The AVR ISP dongle costs 24 dollars at digikey... easy programming through the serial port

You can find a lot of premade libraries on www.procyonengineering.com written by pascal stang who works with bill verplank at stanford.

download winavr.sf.net and you are ready to go....

try http://www.avrfreaks.net for tips and tricks about ATMEL processors.