Google's new online book repository has gone online, and includes a few books about our favourite creature.
Where Bigfoot Walks - Robert Pyle
Yeti Or Not, Here We Come: Bigfoot in the Redwoods by Robert Steven Leiterman (Kids fiction)
Bigfoot - Michael Burgen (kids fiction)
The Archetype of the Ape-Man: The Phenomenological Archaeology of a Relic Hominid Ancestor by Dawn Prince-Hughes
The Klamath Knot by David Rains Wallace
There are a few more - I'll add them when I get time.