Here are some links to other sites I have visited and found useful.
MSTS Sites
http://www.uktrainsim.com
The best site for UK image addons fot MSTS.
http://train-simulator.sebastianfrey.de/
A good site for rolling stock, especially German pieces.
http://www.train-magazine.com/
A lot of downloads for US and European outline stock.
http://www.trains-station.com/
this site has many Dutch outline locomotives and stock and is regualrly updated.
http://www.trainsimbelgium.cjb.net/
A good site for Belgian trains for MSTS.
http://www.kimsim.co.uk/pages/kimsim.htm
Some excellent British trains, and more in the pipeline.
http://www.train-magazine.com/spaintrains.htm
The home Spaintrains covering Spanish stock and Engines.
http://members.liwest.at/shob/mstse.htm
A good site for Austrian items, as well as some Swiss.
http://mstsdk.cjb.net/
The site for the Northern Danish Route.
http://www.train-sim.dk/
Danish Train-sim Site, has lots of Danish Outline stock.
http://www.eto-software.de/
Webpage for the "Activity Analysis" program.
http://ajtrainsim.free.fr/
A French MSTS page, currently a few good downloads here, and some more on their way according to the site.
http://train-simulator.startkabel.nl/
An excellent Portal Page for MSTS.
http://www.ifrance.com/crogiez/
Philippe Crogiez's webpage, sadly most of the files are only available by ordering his CD.
http://www.trainsim.ru/en/index.shtml
The Russian Train-Sim site, lots of good activities to use the Russian stock on this site.
http://www.aluminumcloud.com/
Eric Joiner's site, lots of excellent reskins for the F7 from 3dtrains.
http://www.3dtrains.com
The site for the F7 and GP9 from the creators of the same name.
http://www.auran.com/trainz
The site for the makers of Trainz, also has some free stuff for MSTS
http://www.angelfire.com/games3/trainsim0/downloads.html
Lots of Canadian stock here.
http://www.christrains.com/
The site for Chris Longhurst's excellent Dutch outline stock
http://free3d.dekosoft.com/
Some free and some commercial North American Diesels
http://www.railserve.com/Computers/MSTS/
Railserve has a great wealth of downloads, but sadly a restricted daily limit.
http://www.3dtrainstuff.com/
Another site with both commerial and free items, including the commercial Tehachapi Pass Route.
http://web.ukonline.co.uk/markshipman/railway/msts/msts.htm
Some excellent Britsh image diesels here, including DP2,Class 40, and DP1 in progress.
http://cpr.railfan.net/CPMSTS/
Another good site for Canadian stock
http://www.geocities.com/conbuilder/
The website for the "Conbuilder" program.
http://www.railwaystation.com/trainsim/
A site where you can download some Great Northern stock
http://www.mikemad.de/msts.htm
Madmike's site, which has German image stock including a Prussian P10 in development.
http://freepages.hobbies.rootsweb.com/~agene/
Mike Simpson's site which has an LNER Garratt for download.
http://www.trainartisan.com/files.htm
The site for the excellent Empire State Express trainset.
http://www.railpage.org.au/steam4me/trainsim/
A site with Australian image stock including a superb Garratt.
http://mstsuk.tripod.com/
This site has some skins for MSTS wagons.
http://www.howintheworld.com/downloads.shtml
This site has a patch that greatly improves the train selection menus in MSTS.
http://www.tillier.net/speedworks/index.html
This is the site for the commercial TGV release.
http://msts.e-buzz.net/
Many Swedish outline items can be found here.
http://home.wanadoo.nl/wjnijhof/
The home of the Hoogdam Route.
http://www.mnwright.freeserve.co.uk/train/train.htm
The page for the very useful TGAtool.
http://users.skynet.be/bs134418/site/default_en.html
MS Trainstop site, some good European items here.
http://www.virtualrails.com/mstsrailyard0901.htm
A good site for MSTS news.
Real Railways
http://crcyc.railfan.net/
The Conrail Encyclopedia.
http://66.150.121.21/
The Reading and Northern Website
http://mswurst.50megs.com/
the "Idiot Railfan" site.
http://members.tripod.com/~Class33/
A site dedicated to the British Class 33 "Crompton".
http://espee.railfan.net/
A site dedicated to the Southern Pacific Railroad.
http://sptco.railspot.com/
A site dedicated to the Southern Pacific Railroad's Depots and Structures.