I was first introduced to timelapse photography when I
joined a team doing a documentary on North Cascades glaciers. Timelapse is a great way to add a dynamic aspect to photography.
What are timelapses? Timelapses are created by taking a series of still photos and stringing them together to show a fast-forwarded version of how the captured scene changes with time. In this way, hours of real-time can be compressed into mere seconds of film. The fast-forward speed is dependent on the interval between photos and the frame rate at which they are played.
What you will need: (1) A camera. Can't take photos without that. (2) A tripod. So that every photo captures the same frame so the video flows smoothly. (3) An intervalometer remote that connects to the camera to take a sequence of photos on a set interval. Otherwise you have to just stand there pressing the shutter button manually for hundreds of shots. (4) Computer software to merge the photos into a standard video file (usually at a frame rate of 15-30 frames/sec); there are several simple programs available for free download (I use MPEG Streamclip or Time Lapse Assembler).
The math. The engineer in me likes the mathematical side of timelapse. But don't worry, the math is simple. Say you want a 10 second video; using a frame rate of 24 frames/sec, this video would be comprised of 240 still photos. The following table gives examples of how long you need to run the timelapse and rough guidelines for the interval between photos, depending on the lighting situation. Note that these are only examples, as a timelapse can be made up of any combination of interval, frame rate, and number of photos, it's up to you!