Open the power plant window, and then close it with the X button in the top right hand corner. Now open the Rewards and opportunities window, and then close it with the X. Now open the Garbage disposal window, and close it with the X. And Finally, open the Landmarks window and you'll have every building in the game.

Gives all the reward buildings cheat:
While playing press ctrl-alt-shift-c and a dialog box should appear.
Type in "pay tribute to your king" and it should give you all the reward buildings. Note: sometimes this code doesn't work if you have a lot of reward buildings already placed.

Cheats:
Note:These codes are case sensitive!

let's make a deal - neighbor/business deals offered
i like red tape - all ordinances become available
nerdz rool - high tech industry

CODE: i am weak
EFFECT: Makes buildings, utilities, zoning, transportation, planting trees and creating surface water free.

CODE: call cousin Vinnie
EFFECT: A new petitioner item will appear in the Meet window, announcing a "Local Fundraising Event."
This, um, "businessman" will offer you some cash, no questions asked.
Should you choose to accept his offer, you'll notice a little extra cash in your piggy bank.

CODE: zyxwvu
EFFECT: This code isn't available to just anybody, you have to prove your integrity first.
Use the "call cousin Vinnie" cheat and refuse his immoral offer.
Then use the "zyxwvu" cheat and the beautiful SimCity Castle will appear in your Rewards menu.
In addition to looking cool, the castle boosts land value, aura, and does other wonderful things to the surrounding area.

CODE: garbage in, garbage out
EFFECT: Makes all garbage buildings available.

CODE: power to the masses
EFFECT: Makes all power buildings available.

CODE: water in the desert
EFFECT: Makes all water buildings available.

CODE: Salt on
EFFECT: Changes the sea to salt water.

CODE: Salt off
EFFECT: Changes the sea to fresh water.

CODE: Terrain one up
EFFECT: Raises the terrain.

CODE: Terrain one down.
EFFECT: Lowers the terrain.

CODE: Terrain ten up
EFFECT: Raises the terrain.

CODE: Terrain ten down
EFFECT: Lowers the terrain.

CODE: UFO Swarm
EFFECT: After typing the cheat code, Set Disaster to UFO and watch an
extreme number of flying saucers descend upon your city.

CODE: The Birds
EFFECT: Look closely for a flock of seagulls flying above your fair city.
And tell your Sims to cover their heads.

CODE: nerdz rool
EFFECT: Causes clean, hi-tech industry to be built in your Industrial Zones.

Simon Says
EFFECT: The following codes cause the Newsticker to display something unusual.

CODE:
fund
advisor
moremoney
maxis
1234
sc3k
mayor
hello
simcity
money
ticker

SimCity 2000 music
Note: This procedure involves editing a game file; create a backup copy of the file before proceeding.
Use a text editor to edit the "audio.ini" file in the "/game/res/sound" sub-directory in the game directory.
Locate the "SimCity 200 Theme" line in the file.
Change the numbers that follow that entry from "0,0,0,1" to "0,1,0,1".
The music from SimCity 2000 will now accessible during the game from the preferences screen.

Import unlimited money
Note: SimCity 2000 is required for this trick.
Create a city within SimCity 2000 using the "More money" cheat in that game.
After accumulating enough money, save and exit the game.
Start SimCity 3000, click "Load City" and load the recently created SimCity 2000 city.
You will have the desired terrain with the money.