Fly to the Moon (virtually)
The code used by the guidance systems of the Apollo command module and Lunar module is now available as public domain executable code after the developers of the Virtual AGC and AGS project scanned and transcribed the hard-copy versions from the MIT Museum. Virtualagc, a project that creates emulators of the flight computers of Apollo, allows developers and others to look at the technology that helped take men to the Moon forty years ago.
The emulator is not a flight simulator, but an accurate recreation of the functionality of the computers which were installed in the Apollo vehicles. It recreates the keypad and display panels which the astronauts used to navigate and land the Lunar module.
The source code, including the original comments, is now hosted on Google Code. Google are promising to add an extension to syntax highlight the code for easier reading. The emulators are available under the GPLv2 while the original Apollo code is in the public domain.