I remember on the trip home on Apollo 11 it suddenly struck me that that tiny pea, pretty and blue, was the Earth. I put up my thumb and shut one eye, and my thumb blotted out the planet Earth. I didn’t feel like a giant. I felt very, very small.
– Neil Armstrong 
On this day 40 years ago, the Apollo 11′s Eagle lunar module landed on the Moon. As Neil Armstrong and Buzz Aldrin became the first humans to walk on the lunar surface, Michael Collins orbited the Moon inside the Columbia command module, experiencing “an aloneness unknown to man before”, as aviator Charles Lindbergh put it .
The Apollo program was an enormous technical achievement. I shall forever be amazed at how the engineers who worked on this program managed to accomplish so much with the technology they had available at the time. The rocket engine was a relatively recent technology back then, the transistor had been invented in 1947, the integrated circuit had been invented in 1958, and the microprocessor had not even been invented yet. In particular, the Apollo Guidance Computer (AGC) was a wonderful work of ingenuity: it was the world’s first modern real-time embedded system, and it led to the development of fly-by-wire systems.
To commemorate the 40th anniversary of the Apollo 11 mission, the command module code (Comanche054) and the lunar module code (Luminary099) have been transcribed from scanned images by the Virtual AGC and AGS project!  The code can be found here.
For example, take a look at the following modules: ascent guidance, Kalman filter, master ignition routine. Yes, programming the AGC seems to have been a spartan endeavor! ;-) If you happen to dislike vintage assembly programming languages, take a look at the yaAGC code, which is written in C.
 The Greening of the Astronauts, Time Magazine, December 11, 1972.
 Robin McKie, How Michael Collins became the forgotten astronaut of Apollo 11, The Observer, July 18, 2009.
 Nathaniel Manista, Apollo 11 mission’s 40th Anniversary: One large step for open source code…, The official Google Code blog, July 20, 2009.