Links

Hardware and Integration
Flightstore (flight control hardware and avionics)
FSUIPC (hardware integration software)
GoFlight (avionics modules)
Leo Bodnar (interface cards and switches)
Maplin (electronic components)
Mouser (electronic components)
Rapid (electronic components)
Saitek (flight control hardware)

Cockpit Builders' Forums
AVSIM
FlightSim
MyCockpit
simFlight

Software
FSInn (VATSIM client)
SquawkBox (VATSIM client)
VATSIM (online multiplayer environment with real ATC)
VATSIM UK (UK region of VATSIM)
VoxATC (offline voice controlled ATC)
VoxATC UK (VoxATC with UK specific phraseology added)