On 5 September 2007 is when AMD let me exclusively deliver news to the world on Phoronix of the new Catalyst Linux driver. (The driver wasn't publicly released that day, but5 September was the day given to myself and Phoronix for no longer being under embargo for breaking the news to the Linux world.)
For nostalgia, those breaking articles were AMD 8.41 Display Driver Preview, ATI R300/400 Linux Performance, ATI Radeon HD 2900XT On Linux, and Shuttleworth On ATI's New Drivers.
The "fglrx 8.41" release stream is what brought the new code into the Catalyst Linux graphics driver for public consumption. With this release the performance was much-improved over older Linux driver releases, finally introduced R600 series support, and brought many new features (eventually CrossFire and other technologies made its way to Linux). It also wasn't until this new code-base that AIGLX support was added. The Catalyst Linux driver still faces its share of criticism these days, but the changes introduced in September 2007 set the stage for a much better driver compared to going back further.
Oktoberfest has come for ATI Linux. It was one day later on 6 September 2007 that I was then publicly allowed to share with the world the details of AMD's open-source strategy, but there will be a separate Phoronix article in the morning to provide a recap.
Official celebrations for the Linux driver milestones will happen later this month at XDC2012 Nürnberg.