I can also provide some useful links to the Total War games series as well and here can you find more news about modding.
http://forums.totalwar.com/
- http://forums.totalwar.com/showthread.php/124-The-Medieval-Total-War-and-Viking-Invasion-FAQ
- http://forums.totalwar.com/showthread.php/118-Frequently-Asked-Questions-amp-Game-Fixes
- http://forums.totalwar.com/showthread.php/119-Frequently-Asked-Questions-and-Game-Fixes
- http://forums.totalwar.com/showthread.php/46-A-guide-to-the-guides-%28Empire-Total-War%29
- http://forums.totalwar.com/showthread.php/263-Guide-to-the-Guides-%28Napoleon-Total-War%29
- http://www.twcenter.net/forums/forumdisplay.php?f=735
- http://www.twcenter.net/forums/forumdisplay.php?f=736
- http://www.twcenter.net/forums/forumdisplay.php?f=1549
- http://www.twcenter.net/forums/showthread.php?p=9871125#post9871125
- http://www.twcenter.net/wiki/Released_Mods
- http://www.twcenter.net/forums/downloads.php
- http://www.twcenter.net/wiki/Modding_Portal
- http://www.twcenter.net/forums/forumdisplay.php?f=734
- http://www.twcenter.net/wiki/Released_Mods
- http://www.twcenter.net/forums/showthread.php?t=483527
- http://www.twcenter.net/forums/showthread.php?t=92488
- http://www.twcenter.net/forums/showthread.php?t=477691
- http://www.twcenter.net/forums/showthread.php?t=477898
- http://www.twcenter.net/forums/showthread.php?t=443435
- http://www.twcenter.net/forums/forumdisplay.php?f=25
- http://www.twcenter.net/forums/showthread.php?t=406671
- http://www.twcenter.net/forums/forumdisplay.php?f=1448
- http://www.twcenter.net/forums/showthread.php?t=136409
- http://www.twcenter.net/forums/forumdisplay.php?f=1695
Mod recommendations
Lord Kaelin - http://www.twcenter.net/forums/forumdisplay.php?f=127 for Rome Total War, http://www.twcenter.net/forums/showthread.php?t=374565 for Medieval 2 and http://www.twcenter.net/forums/showthread.php?t=417435 for Medieval 2
Nefarious One - http://www.twcenter.net/forums/forumdisplay.php?f=867, a massive M2:Kingdoms mod
Elrond - http://www.twcenter.net/forums/showthread.php?t=341088 for Empire Total War
uberbanna - http://www.twcenter.net/forums/showthread.php?t=453038
Medivh - http://www.europabarbarorum.com/ (EB2 is WIP)
DarkOneVenzar has a tool for managing your Medieval2TW mods. Thanks for sharing this M2TW-mod tool.
For those who need to simplify the installation and removal of mods from their Medieval 2 launcher check out http://code.google.com/p/medieval2modinstaller/ program I wrote which makes it a bit easier. Despite the name the program doesn't actually install the mods, just installs them to the launcher. You do need the .NET 4 framework installed, but the client profile version works just fine.
How to install mods on Steam versions
Install the mod into this
if the installation has more than one setup file just install it into the same folder like the first one and patches too
Since http://www.gamesas.com/index.php?/topic/1305493-total-war-discussion-3/page__view__findpost__p__19788436 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
- Shogun TW
- Empire TW
- Napoleon TW
- Shogun 2 TW

However the strategy aspect IS very good IMO, especially in later games where a province has a major city as well as several smaller locations like ports, towns and special buildings like universities thus you have to distribute your units carefully in order to protect them (Napoleon did this best...Napoleon did a lot of things best
). It's a very nice series from almost every aspect (though some installments could work on historical accuracy).
This is in stark contrast to games that are set in earlier eras where one tends to hurl their forces into combat because a disorganized melee will eventually form no matter what. Maybe it's just me but Napoleon really hit the spot, interestingly Empire remains my least favorite installment even though one can argue it's similar to Napoleon. 