I recommend purchasing a BIOS Savior device however the BIOS Savior is not in itself a programmer. Fortunately, you can use the Flashrom utility ( http://linuxbios.org/Flashrom ) provided for in the LinuxBIOSv2/util/ directory.
If things go terribly wrong (and they will if you try long and/or hard enough), you still want an external programmer, it's the ultimate safety net against bricking your boxes. A BIOSSavior (or any other way to program the flash in-system in a system that won't boot correctly) is very nice during development of course, but not strictly necessary, you can pull and program flash chips all day if you have too ;-)
Segher