The Aerotrain is an interesting transportation idea currently being prototyped by Yasuaki Kohama and his group at Tohoku University in Japan.
The basic idea of the Aerotrain is to create a "levitating" train by using the aerodynamic principle of ground lift -- a phenomenon which boosts the lift of a wing when flying close to the ground. This makes it possible to achieve many of the advantages of a maglev train, without the expensive coils. A practical system could fly at speeds of 500km/h, while consuming about 1/2 to 1/3 the energy of the bullet train. The current goal of Professor Kohama's group is to complete a 350 passenger craft with a speed of 500km/h by 2020.
There is also a Quicktime video of the prototype here.
-- by JD