As of writing this there isn't much of an active TA community left which is no surprise for a game that old. There are still many TA related sites to be found on the Internet but just like this one most of them are mere archives now. Some sites are listed here for historical and nostalgic reasons only, because back then at TA's peak they were important hubs for the community, other sites because even in their frozen state they still provide valuable information and tools.
Judging by their forum and news page state TAUniverse now seems to be the only TA site left which deserves the label community hub. Which is no new role for TAUniverse since it was probably the most influential TA site back in the old days.
This is the original site of the guys behind the most important TA 3rd party add-on ever developed and published - the TA Demo Recorder.
Back in the old days these swedes were also known as very skilled TA players in the TA online community.
TADRS is where to find the largest online library of recorded TA games. As of writing this the last game review is eight month old. So the site doesn't seem to be completely dead, at least when applying the scale for games so old like TA.
Recording and watching games is not a feature built into OTA. Therefore you need to install the 3rd party add-on TA Demo Recorder first before you can watch a game you download from TADRS.
Switeck's site is mainly of interest for people looking for a kind of TA patch 3.2 that was never released by CDE. OTA, even when updated with the last official patch 3.1c, is still plagued by a lot of bugs. While your chances to fix game engine bugs without having access to the game's programming source code are going towards zero one can still fix some of the soft bugs since those are caused by badly scripted units and screwed unit data in the according definition files.
And that's where Switeck's TA Bugfix comes in. He put a lot of work into revising the definition files and fixed such famous TA flaws like the advanced CORE construction kbot which tends to abort build queues after a task has been completed (the need to constantly monitor those guys drove more than one player crazy) or the Pelican bug that causes missles to target their feet under the water surface rather their body - which renders missles pretty useless against Pelicans so long as they are in the water and you don't manually force target their fire.
Also, his work on TA Bugfix has given Switeck a deep insight into the way TA stores its dynamic configuration data so you will find a lot of useful hints on how to re-assemble all those configuration files so they need less room and help to load TA faster. On a not so fast computer with few disk space available this information will be very valuable.
One problem with TA Bugfix (and any other MOD) is that you may not find many players online who have it installed. There are reliable ways to switch between OTA and TA Bugfix as needed though, thus this shouldn't discourage you from using this MOD.
This site's TA GUIDE section contains probably the most comprehensive TA game engine mechanics analysis and description ever assembled and published outside of CDE.
Also, the site's unit database covers most of the OTA units and is organized in a quite interesting way: rather than just stating the sole statistic facts it provides a cost/efficiency based analysis for each unit too.