It was 30 years ago today that Richard Stallman announced something kind of crazy: he was going to initiate a project to implement a version of the Unix operating system that was completely free (as in freedom). He called the system GNU (GNU's Not Unix) and his original announcement is preserved here as a piece of IT history.
GNU is highly significant for FLOSS fans. It was the first project that consciously and clearly set out sharing of source code as a basic principle. The Free Software movement didn't yet formally exist in 1983, but Stallman went on to become a key figure in its formation as time went on. GNU itself became a key component of the Linux operating system.
If you want to learn more about GNU, go over to gnu.org and read up on its history and the philosophy behind it all.