By Rail & Bus
All trains to Fort William and Mallaig go via Glasgow train station. Best bet to make your own arrangements http://www.firstgroup.com/scotrail/index.php or telephone 08457 48 49 50. The train journey is spectacular and Wanderlust Travel Magazine in 2010 recently voted the line from the Fort to Mallaig as the best in the country beating off stiff competition from the Orient Express, now that takes some beating!
Travelling from London is very comfortable on the overnight sleeper, visit the above link at Scotrail for time tables. Trains travelling from London stop in Fort William. Here you pick up a connection for Mallaig.
Steam Train “The Jacobite”
In the Summer months, travel back in time on the Steam Train Jacobite http://www.steamtrain.info/ Cross the famous viaduct just like that famous little wizard on his way to Hogwarts!
Check out the bus connections http://www.citylink.co.uk/ There are no train connection from Inverness or Aberdeen i.e east coast Scotland through direct to Mallaig, but excellent bus connections.