The 11th has special significance for me. Yes, beyond the obvious one. No, it has nothing to do with the planes. In fact, it happened hours before the Trade Center was hit.
The significance of 9/11/2001 for me is that it's the date of my first contribution to Open Source.
A little after midnight, Simon Cozens, who was then the release manager for Parrot, released the first version of the source. He said that one of his priorities was for someone to write a Perl script called Configure, which would probe the system it was running on and determine a few things about it. Parrot would use this information later.
I had a working version by 2 am, and I received the message at 2:30: "Thanks, applied. Now go to sleep. :)"
Since then, I've contributed a great deal to Parrot--Configure has grown dramatically, and I've written several other systems. But September 11th marks the day I became an Open Source hacker.