hey
while it is not open-source, AVR Studio 4 and the AVRISP do a good job of burning the booloader on Atmega8's and 168's. This is what Gianluca, the manufacturer of the Arduino uses to burn the retail version. I was having problems with a mishmash of some of the methods described above, until I just ordered an AVR-ISP mkII from digikey for about $40.. now it is a snap. Just my 2¢...
Here's a tutorial outlining the above process...
D