I don't know whether it's been mentioned before, but since I seemed to have broken one of my Arudinos (a SB Freeduino, actually), I was prodded into figuring out how to burn a new bootloader onto the arduino chip.
I have a rather ancient Atmel STK500v1 programmer, and a Mac, so it wasn't immediately obvious that I'd be able to get anywhere.
However, the following setup seemed to work:
Mac, prolific (? p2303) USB/Serial interface, rs232 cable, STK500 in ISP mode. ATmega168 in "green" 28pin socket.
I started by playing with avrdude explicitly, which was good since I also started with a keyspan usb adaptor that wouldn't do 115200bps, and that DIDN'T work. However, once I switched USB adaptors and dumped the old (broken) flash contents for possible debugging, I decided to see if the arduino environment would handle the task. After all, everything claimed to be using "stk500 protocol", and the details of the physical connection should have been more-or-less invisible...
In short, it worked fine. I set up the serial port appropriately (with it connected to the stk-500), told it to burn the bootloader using "AVR ISP", and it proceeded to do its job with no problems. I suppose I COULD have used the cable form the STK500 to the actual Arudino without swapping chips around, but it didn't occur to me that things would be so easy....