The Coreboot project was previously called LinuxBIOS and development of it began more than a decade ago. In that time, there's been great progress, but it's still rare to actually see Coreboot in the wild. AMD has pledged to support Coreboot on all future CPUs, a pledge they made just last month, but for years now they've been contributing engineering resources and documentation on their processors and chipsets to make this work possible. Some of their past drops have included Coreboot support for Fusion, RS780/SB700 documentation, and other chipset specifications.
Beyond AMD's support, various motherboard vendors have contributed in some manner, such as Tyan and Gigabyte. There's also other big names associated with Coreboot, such as Google and the CME Group, but still it's not too common yet to find Linux users ridding their systems of a proprietary BIOS.
For those interested in this major open-source BIOS project, there is a list of supported motherboards. The good news though is that at least one major OEM is preparing to ship Coreboot on select products beginning late in Q3 (September) or in Q4 (October through December) of this calendar year. This is information I have received from a reliable source that's at Computex Taipei this week. Details about the planned Coreboot deployment are still being worked out.
More information on this interesting project can be found at Coreboot.org. Beyond being 100% open-source and free, Coreboot prides itself upon its boot speeds and its vast support of different motherboards/chipsets and payloads.