http://www.ibiblio.org/obp/index.php
I am thinking about sometime in the distant future finding a digitized version of some old, public domain math books, preferably modern algebra or linear algebra, and augmenting them with explanations that I wish I had had when learning the stuff. Anyone know where I might find a digitized, public domain algebra book?
-- BayleShanks
Maybe ask at the math songs wiki [1] or latex wiki [2]
The idea of collaboratively authoring textbooks is also addressed by the WikiMedia Foundation's Wikibooks project, http://www.wikibooks.org/