Merge pull request #1596 from mistermatze/cs-unplugged

Add CS Unplugged: Computer Science without a computer

free-programming-books.md

@@ -259,6 +259,7 @@ Original Source: [Free Programming books](http://stackoverflow.com/revisions/392
 * [Animated Algorithm and Data Structure Visualization](http://visualgo.net/) (Resource)
 * [Binary Trees](http://cslibrary.stanford.edu/110/BinaryTrees.pdf) (PDF)
 * [Clever Algorithms](http://www.cleveralgorithms.com/nature-inspired/index.html)
+* [CS Unplugged: Computer Science without a computer](http://csunplugged.org/books/)
 * [Data Structures](http://www.cse.iitd.ernet.in/~suban/cs130/index.html) - Prof. Subhashis Banerjee, IIT Delhi
 * [Data Structures and Algorithms: Annotated Reference with Examples](https://drive.google.com/file/d/0B48k2jhdQ5P2aVlmMFB1UUJLczA/edit?usp=sharing)
 * [Data Structures Succinctly Part 1, Syncfusion](http://www.syncfusion.com/resources/techportal/ebooks/datastructurespart1) (PDF, Kindle) *(Just fill the fields with any values)*