According to SoundtrackNet it is by Steve Jablonsky who also composed the score for the movie.
Hi ZombieKlown,

It is indeed a great song. It's also used as the main menu music for the Steamboy DVD.

Anyway, it's called 'Full Force', and was composed by John Powell. The tune is part of a CD called 'Directors Cuts - Audio Trailer'. Unfortunately this CD is not available to the general public. Only those who can obtain a valid license and can afford the royalty costs will be able to sample the delights of such compositions.

However... send me a private message if you REALLY like the song. ;)