General Flight Simulator Sites

AVSIM Online Avsim Online has all that the flight simmer could possibly want. Avsim Online has a vast number of downloads that grows each day, forums, reviews, news and online shopping.
FlightSim.Com FlightSim.Com is arguably one of the most popular flightsim sites. They have has a vast number of downloads that grows each day, forums, reviews, news and online shopping.
SAVAS - South African Virtual Aviation Services SAVAS is a South African based site. They have South African related downloads for aircraft and scenery. They are also a very good source for South African aviation information. Closed.
Simviation.com Simviation is another very popular download site and has lots to offer. They have the same type of services as Avsim and FlightSim.Com.

Aircraft Model Developers

AFG - Allied FS Group AFG have produced fantastic NAMC YS-11 and Caravelle III packages with a very good panel and sound packs included. For new projects and updates visit their site.
Contrail-Designs
Contrail-Designs was a new group developing the de Havilland Dash 8 range and many more wonderful projects but has since closed down.
CSI - Creative Simulations International CSI are known for making highly realistic models. They no longer exist and their site has since been shut down.
David Maltby Flight Sim David Maltby has produced some truly wonderful models based on old British and European aircraft like the de Havilland Comet, Hawker Siddeley Trident and Vickers VC-10.
Dreamwings Dreamwings have produced some wonderful planes so far with their Fokker 50, Embraer ERJ-170, ERJ 135 - 145 series and their Dash 8 Q400. They have since shut down as a group.
FlightFX/SGA/Kittyhawk FFX/SGA/Kittyhawk have produced a number of excellent models including a Boeing 727-200, 737-200, 737-800, DC-10 and the MD-80/DC-9 variants. Their site has been shut down.
FlightSimOnline FlightSimOnline have released lots of wonderful planes like their Dash 7, AC Commanders, Howard 500, Beechcraft D18 and the recently released Spartan.
Historic Jetliners Group
Historic Jetliners Group has been around for many years now and has focused on the old classic jetliners like the Boeing 707 and the DC-8 ranges to name a few. Forum.
iFDG iFDG have made lots of great planes from their early Boeing 757's and 767's to their newer MD-11's and more recently their superb Airbus A320 range. Forum.
MelJet Melvin Rafi produced an excellent Boeing 747-400/F and Boeing 777-2/300 with unbelievable detail for FS2002. Unfortunately he has been inactive for some time now.
Mike Stone's Hanger Mike Stone has produced a very wide range of aircraft. His Beechcraft 1900D is of my favourite planes. He has since retired from the FS community.
Mirage Aircraft for Flight Simulator Here you can find a collection of possibly the best Mirage jet fighters available on the internet as well as verious other great resources.
Project Airbus
Recently relaunched, Project Airbus is currently remaking its A320 range and have just began releasing their superb models. New projects being developed. Forum.
Project Fokker Project Fokker have produced a beautiful model based on the Fokker 100/70 range and have released an updated version a while ago as well as the superb new Fokker 28 range.
Project Open Sky Project Open Sky have produced outstanding Boeing 747 V4, Boeing 757-200, Boeing 767 V4 and now Boeing 777 V2, Airbus A330-2/300, Airbus A340-2/300, and many more. Forum.
Rick Piper Paintshop Rick Piper has produced a number of turbo-prop aircraft including the Vickers Vanguard, Viscount and HP Dart Herald. Busy updating Vickers Viking and BAe/HS.748 and more.
Vista Liners
Erick Cantu has since retired from making models, but latest releases include a truly wonderful Boeing 727 range and a beta version of his L-1011 Tristar. Forum.
YeoDesigns Home Page YeoDesigns produced an excellent Boeing 737-200 for FS2002 and merged with AFG - Allied FS Group just before shutting down as a group.

Misc

Airliners.net Here you will find photographs of practically every aircraft and livery that you can imagine. From black and white to the most recent digital photos - it's all there!
MW Graphics Martin Wright has made some excellent programs including DXTBmp which I use to create my repaints. There are many other very useful utilities to choose from.
Microsoft Flight Simulator Microsoft Flight Simulator FSX homepage - has not yet achieved the same popularity as Microsoft Flight Simulator 2004 which most freeware groups still mainly support.