Growing cities:
While playing a game, press [Tab]. Then, type "viagra" at the 
green cursor at the bottom of the screen.

Codes:

CTRL-M - it gives yourself and your company $1 million ea. - 
Brian Whiffen 
Bigfoot - Instant Win 
BoBo - Instant Lose 
King of the Hill - Gives Player $100 million 
Cattle Futures - Gives Player $1 Million 
Powerball - Give company $100 million 
Slush Fund - Give company $1 million 
Speed Racer - Trains go double speed 
AMD103 - All engines are changed into AMD 103s 
Casey Jones - All other companies' trains crash 
Show me the trains - Allows the purchase of any Locomotive 
Viagra - Doubles population 
Let me in - Opens all territories