Added "PDQ: Pretty Darn Quick: An Agile, All-Purpose Methodology"

free-programming-books.md

@@ -346,6 +346,7 @@
 * [Networks, Crowds, and Markets: Reasoning About a Highly Connected World](http://www.cs.cornell.edu/home/kleinber/networks-book/)
 * [Open Government;Collaboration, Transparency, and Participation in Practice](https://github.com/oreillymedia/open_government)
 * [Object-Oriented Reengineering Patterns](http://win.ua.ac.be/~sdemey/) - Serge Demeyer, Stéphane Ducasse and Oscar Nierstrasz
+* [PDQ: Pretty Darn Quick: An Agile, All-Purpose Methodology](https://leanpub.com/PDQ) - Jeff Franz-Lien
 * [PNG: The Definitive Guide](http://www.libpng.org/pub/png/book/)
 * [Pointers And Memory](http://cslibrary.stanford.edu/102/PointersAndMemory.pdf) (PDF)
 * [Programmer's Motivation for Beginners](http://programmersmotivation.com/)