The Lenovo X201 from the Intel Celpella platform (Ibex Peak + Core i3/i5/i7 Clarksfield/Arrandale processors) is now supported by Coreboot as an open-source replacement to Lenovo's proprietary BIOS.
Coreboot has been extensively tested with the Lenovo X201 and works for most functionality but currently fails in handling suspend-to-RAM, ExpressCard hot-plugging, and occasional battery misreporting.
Those with a 2009/2010 Lenovo ThinkPad X201 and want to try Coreboot need the mainline code as of this Git commit that happened early on Sunday. Many details about X201 on Coreboot can be found via the project's Wiki.
If you're looking for a low-cost device shipping with Coreboot by default, check out the Acer C720 Chromebook with its decent Intel Celeron "Haswell" performance.