I just finished whipping up a little article that chronicles the release build numbers and dates for most of the releases of Community Server past and present (this helps folks who are upgrading and unsure what version they have, etc.). I say "most" because there is likely a beta or release candidate (and "private releases") that is missing. Let's just say the documentation process has been lacking over the course of the product lifetime so guaranteeing that you got them all would be very difficult. At any rate, there is a lot there.
So, when did we (Telligent) release Community Server 1.0? The answer to that question depends on if you are looking for the first release of any kind or the first RTM release. If you are looking at the first release of any kind then the answer would be that we released Community Server 1.0 Beta 1 on November 17, 2004. If you are looking at the first RTM release then we released Community Server 1.0 on February 18, 2005.
When the first beta dropped, ScottW had the following to say:
"It's still a little rough around the edges, but the core pieces are in place. We now need to clean up the text, wire up a couple of the features, and hit the bug list at full speed.
As for blogging, I believe it is missing a couple.Text features: Key Words, Atom support, and the SimpleBlogAPI.. All of which should be in the final release (let me know if you find anything else missing :)"
What did these early betas of Community Server 1.0 look like? One word - sweet. Ok, maybe sweet is being really really generous. See "sweet" for yourself below.....

In the words of ScottW, the focus of Community Server 1.1 "...was performance and bug fixes." Community Server 1.1 (seen below) was released on June 16, 2005.
Community Server 2.0 was released on February 20, 2006. Community Server 2.0 ushered in the following major changes/additions:
- the first move in the "unified media" direction with the "file gallery"
- RSS Reader - oh yes, it's true.....we had an RSS reader integrated into the product which was extremely innovative at the time.
- Tablet support in the content editor
- RSS enabled search
- Forum personalization
- Embedded video support in posts
- Member points
Even with a slew of new features, I think the biggest shift with 2.0 was that it ushered in the era of "the add-on" (KenR was busy!). With 2.0 came the following add-ons:
- FTP Gateway
- Enterprise Search
- Email Gateway
- Single Sign On modules
These came along side the NNTP Gateway add-on which was released around the 1.1 timeframe. Email Gateway, in particular, was and remains a game changer because of its ability to merge the worlds of internet/intranet discussions and email discussions.
Here is a shot of a CS 2.0 beta:

There was a lot of movement on the UI between the beta and the RTM. At one point, we lost our minds:

Here is a screen shot of the RTM release of Community Server 2.0:

Community Server 2.1 was released on August 9, 2006 and it brought with it a bunch of new stuff. Some of the 2.1 enhancements included tag support, badges, more reports, enhanced editor, simple content management, content mirroring, and feedburner support. The overall look of the Community Server UI didn't change much in this release.
Community Server 2007 was a beast. We tried everything to get it out the door...including cloning ourselves...

Community Server 2007 was released on April 16, 2007. The biggest "new thing" in Community Server 2007 was probably the Chameleon engine. Chameleon is a template based markup engine that powers most all of the user interface in Community Server today. BenT wrote Chameleon and while it isn't always the easiest thing to grok at first, it is still much better than what we had before. Here is a screenshot of Community Server 2007.
Community Server 2007.1 was released on September 18, 2007. Here is a screenshot of Community Server 2007 SP1:

Community Server 2008 was released on April 15, 2008. Here is a screenshot of Community Server 2008:

Thanks for the pic DanH.
So, there you have it. We've made it all the way to the current release which is Community Server 2008.5 Service Pack 1 which was released on October 29, 2008. It looks similar to Community Server 2008 from a user interface standpoint.
In September of 2008 we launched our newest product called Evolution. Evolution is "Community Server inside the firewall". Evolution has caught on like wildfire! Here is a screenshot of Evolution 1.0:

Evolution has all the great feautures of Community Server but they've been stitched together to make social computing inside the firewall a reality.
We're hard at work on the next version of Community Server v.Next and Evolution v.Next and we can hardly wait to start showing you screenshots of what things will look like. Stay tuned.