"Open Books is an award-winning nonprofit social venture that operates an extraordinary bookstore, provides community programs, and mobilizes passionate volunteers to promote literacy in Chicago and beyond."They have an incredible store with 50,000 books to choose from (but I've heard they're processing more than 350,000) with very affordable options in any genre you can imagine.
Last night I attended one of their volunteer orientations and was impressed by the turnout. The bookstore itself is staffed almost solely by these volunteers. Click here to get a list of ways you can get involved including story time, school visits, book processing, tutoring, etc.
I'm pretty excited about their upcoming event - The Revelry 2010. Here is the brochure: