(I thought i'd share all my favorites saved in my browser for FSX/FS2004, feel free to add to the list. Updated as i find more)

Payware aircraft
A2A simulations:- http://www.a2asimulations.com/
Abacus:- http://www.abacuspub.com/default_fs.html
Aeroplane Heaven:- http://www.aeroplaneheaven.com/home.htm
Aerosim:- http://www.aerosim.co.jp/aero/page1.htm
Aerosoft:- http://www.aerosoft.com/cgi-local/us/iboshop.cgi?show270,5527827690
CaptainSim:- http://captainsim.com/
Carenado:- http://www.carenado.com/CarSite/Portal/index.php
Classics Hanger:- http://www.classics-hangar.de/main_en.htm
CLS:- http://www.commerciallevel.com/
Digital Aviation:- http://www.digital-aviation.de/site/
Eaglesoft:- http://eaglesoftdg.com/index.htm
Fsd International:- http://www.fsd-international.com/Products.htm
Glowing Heat :- http://www.glowingheat.co.uk/
Icarusgold:- http://www.icarusgold.com/FS/news.php
iFly:- http://www.iflysimsoft.com/
IRIS:- http://www.irissimulations.com
LevelD:- http://www.leveldsim.com/sevensix_home.asp
MAAM:- http://www.maam.org/maam_sim.html
Milviz:- http://www.milviz.com/fs/news.php
PMDG:- http://www.precisionmanuals.com/
QualityWings:- http://qwsim.com/index.php/products
Razbam:- http://www.razbamsims.com/
RealAir:- http://www.realairsimulations.com/home.php?page=home
Skysim:- http://www.skysim.co.uk/home.htm
Sky Simulations:- http://www.skysimulations.com/
Sky Unlimited:- http://skyunlimited.net/products.htm
Vertical Reality:- http://www.vrsimulations.com/tacpack.htm
Vertigo Studios:- http://www.vertigostudios.co.uk/
Virtavia:- http://www.virtavia.com/
WilcoPub:- http://www.wilcopub.com/

Payware helicopters
Area51:- http://www.area51sim.com/
Cera:- http://cerasimaircraft.com/
Nemeth Designs:- http://www.nemethdesigns.com/
Dodosim:- http://www.dodosim.com/

Payware terrain/airports/environment
Aerosim:- http://www.aerosim.co.jp/eigo/page1_e.htm
Blueprint Simulations:- http://www.blueprintsimulations.com/index.htm
FlyTampa:- http://www.flytampa.org/
FScene:- http://www.fscene.com/
FSDreamteam:- http://fsdreamteam.com/
Megascenery:- http://www.megasceneryearth.com/
OpenVFR:- http://openvfr.freyt.de/magento/index.php/
Orbx:- http://fullterrain.com/index.html
REX2:- http://www.realenvironmentxtreme.com/
SimSavvy:- http://www.sim-savvy.com/ (thanks to Robmypro)
TeamSDB:- http://www.facebook.com/TeamSDB.scenery
Ultimate Terrain:- http://www.scenerysolutions.com/index.html

Payware boats/ships
Delta Studios:- http://deltasimstudio.com/

Freeware aircraft
Alphasim freeware:- http://www.easyfly.co.nz/Freeware/index.php?
Avsim:- http://forum.avsim.net/index.php?app=ccs&module=pages&section=pages&id=2
Avsimrus:- http://www.avsimrus.com/ (Avsim, but alot of good Russian stuff)
BritSim:- http://www.britsim.com/
California Classics:- http://www.calclassic.com/index.html (thanks to Rick50cal)
CamSim:- http://pages.infinit.net/camsim/
EnigmaSim:- http://www.enigmasim.com/
Flydeervalley:- http://www.flydeervalley.com/private/dv_downloads/
Flyingstations:- http://flyingstations.com/wyvern.html
Freeskyproject:- http://www.freeskyproject.com/files/
FS_KBT:- http://www.flightinfo.jp/FS_KBT/dai.htm
FSX Dornier:- http://code.google.com/p/fsx-dornier-328/ (thanks to Heretic)
Historic Jet Group:- http://www.simviation.com/hjg/main.htm (Dev team attached to SimV)
ISDT:- http://isdt-israel.com/projects/projects.htm
JU-52 Factory:- http://www.ju52-3m.ch/models.htm
Mike Stone:- http://www.gjsmith.net/Mike-Stone/index.htm
Mike Stone's website:- http://www.pmstone.com/ (thanks to awj112)
Mirage4FS:- http://www.mirage4fs.com/miragef1.html
Premaircraft:- http://www.premaircraft.com/index.html
Rarewings:- http://www.rarewings.com/index.mvc?page=home
SectionF8:- http://sectionf8.com/ (thanks to Retsud-Porc)
Sim-Outhouse:- http://www.sim-outhouse.com/sohforums/index.php
Simviation:- http://simviation.com/
SurClaro:- http://surclaro.com
TaskforceFSX:- http://www.taskforcefsx.com/index.html
UKMil:- http://www.ukmil.org.uk/news.php

Freeware helicopters
Eagle rotor craft:- http://www.eaglerotorcraftsimulations.com/index.php
Hovercontrol:- http://hovercontrol.com/

Freeware terrain/airports/scenery
AFG:- http://www.airfieldconstructiongroup.org/drupal/
Freeware scenery:- http://www.freewarescenery.com/ (thanks to Heretic)

FSDome:- http://www.fsdome.com/showpage.php?url=http://www.fscorner.com/library/scenery/41.htm
Ians site:- http://www.ianpsdarkcorner.co.uk/node/39
LHSimulations:- http://www.lhsimulations.hu/
LockOnFiles:- http://www.lockonfiles.com/index.php/files/category/9-fsx-fs2004/
MAIW:- http://www.militaryaiworks.com/
NL2000:- http://www.nl-2000.com/nuke/ (thanks to Legend)
Shepshed:- http://www.shepsshed.com/fsxbits.htm
Tileproxy:- http://www.edtruthan.com/tileproxy/

Freeware panels FSX/FS2004
Marco Spada:- http://web.mclink.it/MC2752/panels/

Freeware driveable/ships/cars
http://www.fs-freeware.net/flight-simulator-downloads/Flight-Simulator-X/
http://www.fs-shipyards.org/index.php?ind=downloads

Repaints
AussieX:- http://aussiex.org/forum/index.php?/index
Flightsimx:- http://www.flightsimx.co.nz/

FSX missions
Code Legend:- http://www.codelegend.com/idealflight/ (thanks to kludger
Flight Simulator X missions:- http://www.flightsimulatorxmissions.com/
Flysim:- http://flysim.us/website/index.html
Four Flights:- http://fourflights.com/ (thanks to Pmike)
Vertical Studios:- http://www.vertical-studios.net/products (thanks to Scylla)

FSX utilities
Dbsim:- http://www.dbsim.com/
EZDOK:- http://www.ezdok-software.com/
FSInventions:- http://www.fsinventions.com/
FSPassengers:- http://www.fspassengers.com/
FSRecorder:- http://www.fs-recorder.net/
Scruffyduck:- http://www.scruffyduck.org.uk/index.html?erro=1
TaskForce FSX:- http://www.taskforcefsx.com/aicarriers.html

Flight simulator specific stores
http://www.fspilotshop.com/
http://flight1.com/
http://secure.simmarket.com/default-en.html
http://www.justflight.com/default.asp
http://www.pcaviator.com/store/home.php?cat=652

Other sites listing FSX/FS2004 aircraft
http://blogs.msdn.com/b/ptaylor/archive/2008/08/31/available-freeware-aircraft-add-ons-and-fsx.aspx (thanks to FAC257)
http://www.flightsimworld.com/forums/index.php?showtopic=118710

waiting to sort
Prepar3d:- http://www.prepar3d.com/

Glad to have made the list. Thank you so much for the support!!!

Kind regards,
Chris

Chris Klein - Vertical Studios

Open source aircraft:
http://code.google.com/p/fsx-dornier-328/


Freeware scenery index:
http://www.freewarescenery.com/

Add Sim Savvy to the payware scenery list. A must-have item IMO.

Mike Stone is developing for FS2004 again. Website is www.pmstone.com. Just put out a B-25 and an IAI Westwind 2.

While there's info available at taskforce FSX, I'd say that AI carriers deserves it's own post under "FSX utilities"

http://www.taskforcefsx.com/aicarriers.html

Updated 5/21/2012

If you see something that's not on here let me know. Share the wealth

WOAI is an absolute must.

www.world-of-ai.com