Growing article, with links to many related topics. Wikipedia.
BIOS Setup Information Guide
How-to guides, general information, upgrades, identifying motherboards, links!
Formerly known as LinuxBIOS, this is a Free Software project aimed at replacing the proprietary BIOS (firmware). Includes a presentation, information for developers and documentation.
Entirely free boot firmware based on coreboot, intended to replace the proprietary BIOS/UEFI firmware. Documentation, download links, source code repository.
Open source implementation of a 16bit X86 BIOS which can run in an emulator or with the use of coreboot. Download links, mailing-list.