Hi. I've been a slacker (actually, I've been in Canada) but I'm back now and crawling out from under a pile of several thousand emails and back into the office (...someday soon. I haven't gone expat yet, SJ) .
While in Vancouver, I visited the Commonwealth of Learning, the folks who brought us WikiEducator. Wayne Mackintosh (who is super-cool), Lauren, SJ, and I had a teleconference on how CoL and OLPC could collaborate, leading to several initiatives including an upcoming Curriculum Jam in... it looks like at least 3 simultaneous locations and growing, and a program similar to Google's Summer of Code but for free and open content. More on this later, I'm sure.
There are many open content projects out there already - for instance, the Open Text Book blog. They've got posts on linguistics, physics, mathematics, electronics, and philosophy already, and you can contribute more if you know of them online. The first post also has pointers to the freetextbooks mailing list if you'd like to get more involved.
While they're working on cataloging existing free textbooks, the Budapest Open Access Initiative is working on making scholarly articles free to catalog. Kuhn's The Structure of Scientific Revolutions calls textbooks and articles the two primary routes of formal communication in academic disciplines - the first for training new members, the second for networking between existing ones - so these two projects are driving at the heart of open content for postsecondary education. (Yes, the XO is designed for younger children - but they've got to have a world of advanced open content to graduate into.)