» Orbiter - A Free Space Flight Simulator    A realistic 3D flight simulator that uses proper physics for the modelling of planetary motion, gravitational fields, free space, and atmospheric flight.    http://www.medphys.ucl.ac.uk/~martins/orbit/orbit.html

» Dan's Orbiter page    Find the module plug-in that enables sound in the simulation. Includes a support forum for frequently asked questions and general discussion.    http://orbiter.dansteph.com/

» Orbit Hangar Mods    A general repository of contributions submitted by third party add-on developers.    http://www.orbithangar.com/

» Orbital Mods    An addon repository focused in the Russian space flight program. It also features a database of known bugs in the simulator.    http://www.orbitmods.com/

» Orbiter In Only One Page    Offers links and files.    http://www.geocities.com/jig_2001/

» Orbiter Mars    Includes concise tutorials that explain the procedures and the planning stage of interplanetary missions.    http://www.orbitermars.co.uk/

» Project Alpha    An ongoing project to simulate the International Space Station Alpha.    http://www.f-a-d.co.uk/

» Saturn's Moons    Includes the major moons of Jupiter and Saturn, missing in the default Orbiter package.    http://www.geocities.com/fastheinz39/Saturns_Moons.html