Tactical Ops Channel - YouTube channel started in 2015 to keep TO:AOT alive with multiple uploaders. Multiplayer gameplay, mix wars and other videos.
333Networks - Server list and master server, displays all servers that query to the master server and manually added servers. (Look for TO340 or TO350 gametype)
GameTracker - Server list on GameTracker, this list only displays servers that have been manually added to the website.
TO:AOT Facebook - Facebook page run by some community members.
Tactical Ops Discord - Tactical Ops Community Discord Server.
TO Wars - TO:AOT website featuring clanwars, ladders and tournaments.
Miau Facebook - Facebook page from the Miau servers.
ESE Protect - Official website from the ESE Anti Cheat for TO3.5. Downloads, documentations, forum for support etc.
UT Files - File Archive with Unreal Tournament related files. Since TO is build on UT99 allot of files are compatible on both. (Mutators, mapvotes etc.)
Unreal Archive - File Archive with Unreal and Unreal Tournament related files.
Unreal Admin - Website with lots of information related to Unreal, UT99 and Tactical Ops server configuration and settings.
Old Unreal - Website dedicated purely to the old Unreal and Return to Napali expansion.
UT99 - The biggest and most active Unreal Tournament 99 community, forums and downloads.
TO2.2 - Community site about the Tactical Ops 2.2 mod for UT99.
TO:Crossfire - Website of the fan made Tactical Ops Mod for UT2004. Sadly the multiplayer scene has died and the server browser is empty.
Smeer Kat YouTube - Playlist with a complete guide on how to create UT99 Maps, the difference between UT and TO maps is very small so it is a great starting point.
Lode's Unrealed Tuturials - Tutorials about Lighting, Movers, Elevators, Exploding Walls, Breaking Glass and more.
Old TO websites
Tactical Square - Archive of the Tactical Square site.
Die Spielwiese - Website from the old german Spielwiese server.
TOSP - The old site from the Tactical Ops Singleplayer Mod.
SuperTeam KeyBinder - Page about the SuperTeam Keybinder.
AIM-IT - Old AIM-IT mapping team website.
Tactical Ops World - Old website from the LST Team.
b33franch Maps - Download page for maps from the b33franch.
Zlodey's Site - Old page from Zlodey with some downloads.
Old websites on web.archive.org
You can modify the date of the website that is loaded, the currently chosen one is mostly random. Try choosing different dates and experiment.