philchute.com/games/team fortress

Team Fortress - Quake mod (Original quake mod)
The original Team Fortress, released as a mod in 1996. This team was hired by Valve to make TFC.
Youtube video: Team Fortress Done Extreme
Youtube video: Team Fortress Done Extreme 2
Youtube video: QWTF - The Redemption

Mega Team Fortress - Quake mod (Expanded class abilities)
Mega Team Fortress features expanded and extended abilities for the nine classes, and was the most widely played form of QWTF until replaced by the streamlined FortressOne. MegaTF is still played on a weekly Friday night game at 7pm EST on gamehost2.tastyspleen.net:27502
Mega Fortress Wiki

CustomTF - Quake mod (Custom class configuration)
CustomTF allows for co-op and pub gameplay with customizable classes which you choose within a budget of money for equipment. CustomTF is played in a weekly pub game every Saturday at 7 pm EST on gamehost2.tastyspleen.net:27507
QuakeWorld Prozac CustomTF website

FortressOne - Quake mod (TFC style gameplay)
FortressOne is an open source fork of the original QWTF played in 4v4 pickups every day on several discords.
The FortressOne client is a stand-alone install based on FTE. This installation is recommended for rather than connecting in the standard FTE installation or ezQuake. Separate installs of the FO client are also great for playing other QWTF games like MegaTF and customTF.
FortressOne Official Site
FortressOne Official Discord
FortressOne Latest Release
FortressOne install video guide
My FortressOne config
My FortressOne clips

Team Fortress Classic
The Quake mod Team Fortress was an early port to the Half-life engine, and is still played to this day, with a small pub community and a diehard pug community.
Video guides: Nuki's TFC Learning Center
Youtube Video: 20th Anniversary Retrospective
Some oldschool skills movies:
Defrag and vriens TFC Skills movie
Skillout - Team Spirit - Plain

Quake 3 Fortress - Quake 3 engine (Splash Damage Team)
Q3F was created in 2000 by the team that would become Splash Damage Studios. It was last updated in 2003 and to my knowledge there are no servers and the mod is not currently playable.
Youtube video: Quake 3 Fortress - The Dark Side

Enemy Territory Fortress - Quake 3 engine (Q3F port)
ETF is a port of Q3F to Enemy Territory. This game is currently playable though no one is playing that I know of.
Youtube video: Enemy Territory Fortress Promo - ETF
Youtube video: Moose & More - ETF Extreme

Fortress Forever - source engine (TFC style gameplay)
Fortress Forever is a source mod inspired by QuakeWorld Team Fortress and Team Fortress Classic and is available for free on Steam:
Fortress Forever on Steam
Fortress Forever Official Site
Fortress Forever Official Discord
Fortress Forever Official Wiki
Fortress Forever Fan Site
Fortress Forever pickup games
Fortress Forever pickup community frag video
Fortress Forever crosshair guide
Fortress Forever config file video guide
My Fortress Forever config
My Fortress Forever clips

Team Fortress 2 - source engine (Valve software)

Classic Fortress 2 - source engine (TFC style gameplay)

Pre-Fortress 2 - source engine (Beta era TF2)

Team Fortress 2 Classic - source engine (2008 era TF2)

Team Fortress 2: Vintage - source engine (2010 era TF2)

Team Fortress 2: Source - Source 2 engine (early era TF2)

Lambda Fortress - Source 2 engine (co-op gameplay)