I have a quick entry to suggest progressive titles to everyone out there. Each of the graphics is hyperlinked to the Amazon.com entry for the book itself. I highly recommend each of these, in no particular order, but would consider the first one, the Lakoff book, absolutely required reading. If you've read something progressive-oriented that I have missed, by all means - please include it in the comments.
Don't Think of an Elephant! George Lakoff
What's the Matter with Kansas? Thomas Frank
God's Politics : Why the Right Gets It Wrong and the Left Doesn't Get It Jim Wallis