I would eventually like to post some of my own personal ramblings about open source stuff, but for now, check out some of the more important documents and websites by other people:
Eric Raymond's The Cathedral and the Bazaar is one of the best books about how and why open source actually works.
Slightly more preachy, but no less important, is Richard Stallman's Free Software Foundation, home of GNU and one of the largest collections of forcibly-free software on the planet.