So what do you want to do if you want to make time-lapse videos? You can buy a commercial intervalometer (yeah, right). You can check out some instructables like this one and make one yourself out of electronic components.
But what if you don't have the time/skills necessary to build one? You just want something quick and cheap.
Well, you can actually use a common TI graphing calculator (I don't know of any high school student without one of these) and hook it up to any camera with a remote shutter release socket. It's quite easy, and depending on your camera can require no electronic work at all.
Step 1: Parts Needed
A TI graphing calculator - I'm using the TI-83+. I haven't tested my code on any other model, so I can't guarantee it will work.
Camera with remote shutter release socket - I'm using the Canon EOS Rebel. This has a 2.5mm socket that you can use to connect to the calculator. If your camera does not have a 2.5mm shutter release socket, you will need to create some sort of link cable that can connect the two together.
Link Cable - If your camera has a 2.5mm socket, you can use the link cable that should come with your calculator.