I can also provide some useful links to the Total War games series as well and here can you find more news about modding.
Official forum - Total War
Total War Wiki
Medieval: TW - Viking Invasion FAQ
Medieval 2 - FAQ and Game Fixes
Rome: TW - Barbarian Invasion FAQ and Game Fixes
A guide to the guides of Empire: Total War
Guide to the Guides of Napoleon Total War
Unofficial forum - Total War Center
Total War Gaming News and Announcements
TWC Publication News and Announcements
FAQ for Shogun 2 Total War
Cannot install or launch Shogun 2 Total War
Discussion about Rome 2 Total War
Discussions about Total War Attila
Released mods
Download mods
Total War Center Wiki
Information about modding
Modding News and Announcements
List of Released Mods on TWC Wiki
Rome Total War
Medieval 2 Total War
Empire Total War
Napoleon Total War
Shogun 2 Total War
Gameplay and strategy for each game
Empire TW
Medieval TW/Shogun TW
Medieval2 TW
Napoleon TW
Rome TW
Shogun2 TW
Rome 2 TW
Other sites about Total War Games
The Assimilation Lab - General
The Assimilation Lab - Tutorial
Medieval 2 Total War - Nexus
I'll update the OP if anyone want to have a list of mod recommendations or solutions of troubleshooting in the OP. Solution Medieval Total War - Gold Edition v2.0.1 CTD Fix
Mod recommendations
DarkOneVenzar has a tool for managing your Medieval2TW mods. Thanks for sharing this M2TW-mod tool.
How to install mods on Steam versions
Since Vaskill mentioned Steam I realize that were no such list of Steam version games in the OP, but below they are listed and let me know if there is something to add or correct that game list.
Retail Version
Medieval TW
Medieval 2 TW
Rome TW
Rome TW Anthology (RTW-Gold, Alexander)
Shogun TW
Steam Version
Medieval TW
Empire TW
Napoleon TW
Rome TW Collection (RTW-Gold, Alexander)
Shogun TW
Shogun 2 TW
Rome 2 TW
Attila TW
Please note that most retail games is also available on Steam, and now also Shogun TW, Medieval TW.