The Transport for London presents this cute Shockwave game on their government website Tube.tfl.gov.uk where you compete to race around a variety of tracks, picking up passengers along the way. There is also a train track constructor set that allows you to set up one of your own designs and race a friend—both using the same keyboard. Race too fast and your train will derail causing a delay. For anyone who has ever been fascinated with model trains, or with riding the London Undergound. Click.
Update: The game has been taken off the site and is no longer available.