Topic says what I mean. A random map generator would be pretty cool. Obviously you'd have to set up some limitations so that it wouldn't create a situation where any bridge is impossible, but eventually it should exist. It could also have control variables for "difficulty", etc.
And leading from that, you could have a multiplayer mode where the generator generates a map, and two players (or more I guess) compete to see who can complete a bridge in the fastest time, or with the least amount of cash, or that can hold the most weight. The last two would have a time limit.