Arturo Camacho's 2007 University of Florida dissertation [pdf] developed SWIPE', a pitch extraction method shown to be superior to all other publically-available algorithms. The dissertation includes MATLAB code [m] implementing the algorithm.
I've created a compiled version of the code in C that is an order of magnitude faster. The current version is swipe-0.95.tar.gz, which compiles on Linux and Mac OS X. Windows is unsupported. See the README and INSTALL files for more information. The LICENSE is free (libre). A Python wrapper is also included.
Please submit bugs and errata to kgorman@ling.upenn.edu. Also see the TODO.