The papers and presentations from the ACM's conferences on the History of Programming Languages. The first was interesting mostly for the historical descriptions of how the languages were created. The second was fascinating because the philosophies behind the languages were so different. The chapters on Lisp, Smalltalk, Forth and C++ were particularly interesting. I now have a hankering to play around with each of them (I never thought I'd want to learn C++, but Bjarne Stroustrup's explanations of why the language features work the way they do makes me want to give it a try). The Lisp chapter reminded me what I loved about coding in Lisp: a mix of programming elegance and humor that I haven't found elsewhere.