So you're making it so you click a button to go to destitnation A. Another for another and so on get in the minecart and you go?(to do the second bit put a stone pressure plate right next to the pushing part and if you boost a minecart it will be on the plate and infront of the piston and so you wire it so when the stone pressure plate is activated it pushed the piston and so when someone gets in it pushed the minecart on to a peice of track next to it, hope this helps :D

Too bad there is no link... Trying to learn to make a better track system for my server :(