Hi,
in the file "arduino-0017\hardware\boards.txt" you can find the sections which fill the "Board" menus of the IDE. There are also the defintions of the bootloader files and the needed fuse settings.
Here the section of the Duemilanove 168:
diecimila.name=Arduino Diecimila, Duemilanove, or Nano w/ ATmega168
diecimila.bootloader.file=ATmegaBOOT_168_diecimila.hex
diecimila.bootloader.path=atmega
diecimila.bootloader.low_fuses=0xff
diecimila.bootloader.high_fuses=0xdd
diecimila.bootloader.extended_fuses=0x00
diecimila.bootloader.unlock_bits=0x3F
diecimila.bootloader.lock_bits=0x0F
diecimila.build.mcu=atmega168
MikeT