I just finished reading a book called Free Culture by Lawrence Lessig. I would highly recommend this book to anyone who wants to gain a good understanding of the debate over copyright and understand how current copyright legislation it is affecting our culture and our ability to innovate. The book is mainly about copyright, but he demonstrates how copyright laws are inhibiting innovation in software. I like the style of the book because he teaches through telling stories about people and events that have been affected by copyright issues. Though Lessig is apparently a little leftist, he effectively shows how the issues affect both sides of the political spectrum.
After reading this book, you may feel the need to become active in the protection of the public domain. A good starting point is to sign this petition. If you live in the U.S., you can then contact your representative(s) in the House and Senate.