This is a step by step build guide to making your own intervalometer on the cheap, allowing you to take timelapse footage.
I filmed timelapse footage before using my CANON A480 compact camera, which was made very easy using CHDK (the canon hack and development kit) firmware hack. How ever I really wanted the footage to be of higher quality so I wanted to use my Nikon D40.
Most low end DSLR's like mine, have an Infrared remote as the sole external trigger. Other cameras may have pre-made wired intervalometers onsale, but these cost hundreds of dollars. Yet the majority of them have IR remote cabability. This means you can buy a cheap knock off, of your camera's remote and HACK 'IT' UP.