If you want to do any sort of motion capture or time lapse photography, the Mumford Time Machine is the gold standard for controllers.
Unfortunately, by the time you get it fully equipped with sensors and camera cables, you are looking at over $400 -- fully worth it if this is what you do but a bit steep for the casual experimenter.
Fortunately, there is the Camera Axe:
Camera AxeThe downside is that you have to have the circuit board made and you need to purchase the components and assemble the project but for someone like me, this is not a downside, this is part of the fun of a project like this. He also publishes the source code so any refinements and changes can be made and resubmitted for other people to use. The circuit boards are made in China. A US company -- Batch PCB -- accepts orders and when they have enough to run a huge batch, the order is placed and ten days later, you get your boards -- total turnaround time is about a month but the prices are cheap! The guy bought everything new and the cost of the unit was about $120. A good scrounger should be able to get that in around $70 (the board is $21 and the display is $25) A project for this winter...
Camera Axe is open hardware and open software project that helps you get some of those difficult to capture photographs. It can use various sensors like light triggers and sound triggers to activate a camera or a flash.
Sunstone Circuits also has a low cost prototype service. A bit pricier than Batch, but they are in the Northwest. I've used them a lot and like their quality and service.
http://www.sunstone.com/