Oh, there's plenty of them out there if you want to use them. Though I personally dislike cheating (see the Are you a cheater??? thread for a discussion) I know a few ways, though I don't use them .
One is to save your game with "multi" in the name. This is VERY powerful and allows you to see the whole map and do a variety of cheaty things, like changing AI production. This was quite recently discovered; you can probably find some discussion threads on it elsewhere in the forum.
You can also go into the editor and change whatever rules you want and save the changed rules as civ3mod.bic (after making a copy of the original, of course). These will take effect in the game. You can do anything from reducing corruption to changing unit stats. Lots of people customize the game using this method.
I believe there are also some utility programs that can help you cheat, though I don't know what they do - again, I don't cheat.
I hope I have been helpful in creating another Civ III cheater (*sigh*). But don't let my tone discourage you - you have a right to cheat in this game...........except in the GOTM, of course.