Remember Dapper Drake? All the fuss around it, being an LTS (long-term support) release, the six-week delay in order to make things stable, all the forum discussions and the enthusiasm with which it was awaited by Ubuntu users.
Dapper Drake was released on June 1st, 2006 and it had version number 6.06. It was probably one of the biggest Ubuntu releases and ended up being known for its stability. After three years of security updates, support for the desktop version of Ubuntu Dapper Drake will end on July 14th, while the server edition will still be supported two more years, until June 2011.
I remember that when Dapper was about to come out I've switched from GNOME to KDE, and I was very enchanted that Kubuntu, the KDE version of Ubuntu, will ship a stable KDE3 environment. For me, that was the most stable Kubuntu I've ever used. In my opinion, after Dapper Drake, Kubuntu never had such a stable release again. A few months later Ubuntu put out 6.06.1, a point release which included several software updates performed after the initial release.
Here's what Dapper Drake included:
Ubuntu 6.06 Dapper Drake
Kubuntu 6.06 Dapper Drake