The Little Book of Semaphores [pdf]
Just coming here to give my usual thank you/plug to Allen B. Downey for all of his wonderfully written (and free!) books. Aside from The Little Book of Semaphores, here are a few of my favorites:<p>How To Think Like A (Functional) Programmer ("Think OCaml") - <a href="http://greenteapress.com/thinkocaml/index.html" rel="nofollow">http://greenteapress.com/thinkocaml/index.html</a><p>Think Operating Sytems - <a href="http://greenteapress.com/thinkos/index.html" rel="nofollow">http://greenteapress.com/thinkos/index.html</a><p>Think Bayes - <a href="http://greenteapress.com/wp/think-bayes/" rel="nofollow">http://greenteapress.com/wp/think-bayes/</a><p>Think Stats - <a href="http://greenteapress.com/thinkstats2/index.html" rel="nofollow">http://greenteapress.com/thinkstats2/index.html</a><p>Also important is his section about how to help free books: <a href="http://greenteapress.com/easy.html" rel="nofollow">http://greenteapress.com/easy.html</a>