Try this out:
http://atmel.com/dyn/resources/prod_documents/novice.pdf
A good not-too-techie intro to the AVR, including a sample project you can run in AVRStudio's simulator. If you want to see the process of writing code (in assembly), this should help you out. The best part is, you can download AVRSTudio and run the sample program while you're waiting for your STK500...
p.s. has anyone tried out avra for an AVR assembler? I've installed it and am about to check it out...