The conch tour train station is just so cute, it made me laugh when I first saw it. You can walk in that little door in the front and get all kinds of great information about the train-ride. You can see where it stops, the Key West attractions it will point out, and can find out if the train will be full or not. Everyone was so nice on the old town Key West train tour.
You can find the Key West Trolley Ride on the corner of Front Street and Duval. It is such a blast and it is the most touristy thing you can do. Rated as one of the top things to do on the island.
This is a daytime only tour, but it would be awesome at night. It would not surprise me if they did a version in the evenings, with less stops than the day trips do.