When you start a game, enter Horza as your 
nickname. Then use any of the following:

Code - 	Effect
Shift + Z - Makes all features available
Ctrl + Z - Makes all rides and attractions available
Alt+ Z - Makes all shops available
Ctrl + C - Increases your funds

Extra money
Note: This procedure involves editing a game file; create a backup copy of the file before proceeding. Use a text editor to edit the "standard.sam" file in the "levels" sub-directory inside the game directory. Scroll down until the "Bank balance stuff" heading appears. Go down a few lines and change the starting balance from "$50000" to any amount.

All worlds
Note: This procedure involves editing a game file; create a backup copy of the file before proceeding. Use a text editor to edit the "global" file in the "data/levels/space" or "data/levels/fantasy" folders. Change "keys.to enter" to a desired number.

World of Wonders park
Collect three Golden Keys to unlock the World of Wonders park.

Space Zone park
Collect five Golden Keys to unlock the Space Zone park.

Easy money
The best way to use this trick is on a puzzle sideshow that has a low play cost. While somebody is playing, up the play cost to $10,000. Make sure that you hit the confirm check to get that price activated. When they finish the puzzle you will get the $10,000 instead of the lower play cost they started playing at.
Nobody will play at $10,000, so lower the price back down to a fair price afterwards. You can do this as often as desired. Puzzle sideshow works best because it gives you time to raise the price while the customer is playing.