Camera sliders help keep the action steady when you move your camera. Commercial sliders can be pricey, but you can build this one with IKEA parts for about $30.
Instructables user DerekMellot put together this build using a cutting board, glider and hook accessories, a triple curtain rail and two ceiling fixtures (used as a mount for the curtain rail to rest on). Check out his Instructable for the full run-down.
$30 IKEA Camera Slider [Instructables]