What's the minimum hardware required for a Mac to burn a bootloader? Macs have no parallel ports, no RS232 ports, just USB, firewire, and the slightly under-utilized ExpressCard 3/4.
I have a Keyspan USB->RS232 dongle, but not sure if that's required or best or irrelevant.
I would say a usb icsp programmer , like the avr mk 2.
Ditto the USB programmer.
I did successfully use a (very old) STK500 with a USB->serial adaptor and avrdude, though I had to find one that supported 115200bps...
The usbtinyisp is pretty popular too.
http://www.ladyada.net/make/usbtinyisp/
And you can also attempt the arduino based isp programmer if you already have a chip with a bootloader:
http://www.arduino.cc/playground/Code/Programmer2