Matewis: Is it possible to sell/buy excess power/water in SC2000? Can't seem to remember
tinyE: WAIT! You can actually do that in 3? I saw the mention of it but I thought the guy was being sarcastic. :P I'm totally serious and evidently I'm totally stupid. XD
You can! :D Though I don't think you can initiate it. If you build a road/railroad/power line/water pipe right on one of the four edges of the map then you will be asked if you want to connect it to the neighbour city for something like 2000 simoleons, which you then connect to your main road/rail/power/water network. The neighbour of that city will then be the one to approach you to make a deal. If you have excess power they might want to buy some, or if you're running low they might offer to sell you some etc. A good way to make some money is to buy their garbage, for which you need a road connection and some extra landfill space. It's quite easy too in 3000, since in 4 from what I can remember landfills cost a lot to maintain. In 3000 you only pay to zone them the first time.