While also very OT, O'Reilly makes a number of it's books available for free online through it's excellent Open Book Program. Here are a couple related to free software.

• Open Sources
• The Cathedral and the Bazaar

And even more off-topic, if for some reason you haven't already read it, In the Beginning was the Command Line by Neal Stephenson is a very interesting read.

Update: I just remembered there's a chapter in Open Sources written by Larry Wall. It wasn't my favorite chapter but maybe mentioning it will make this post a little more on-topic :).

YAU: Free as in Freedom has just been made available online as well.