Atmel AVRs are great, but don't bother with the STK-500. It's OLD! (I have one). Get a
**broken link removed** instead. (I have one too). It's a much more modern design. Like a PICkit 2 on steroids.
**broken link removed**, and works with USB. And it's
inexpensive.
It does JTAG and debugWIRE debugging. AVRs don't debug thru the ICSP cable like PICs. They use JTAG or degugWIRE. JTAG is most common. The STK-500 won't do JTAG or dW as far as I know.
And, so you don't have to have two cables connected to do debugging and programming, you can program the chip via the JTAG connector.
So don't let these PIC guys scare you off AVRs.
They're fun to tinker with too. The instruction set is no more difficult than PIC - really it's probably easier. The architecture is simpler to understand. None of that freaky banked memory. Lots of registers to use (like the newer 16-bit PICs) - not just one W. Nothin wrong with them at all. PICs are just more popular, and not necessarily because they're better.