Long exposures are a great way to play with light trails, and “paint” with light. By letting your shutter stay open for a longer period of time, you can use any light emitting device to creatively ad light to your scene. Remember this technique works only if the camera is on a tripod, and some sort of cable release or timer is used to eliminate camera shake.
The blue lines in the photos bellow are made by a small light up Frisbee. Glow sticks and flashing lights on strings create beautiful multi-colored designs. Flashes set off randomly in a field can create the illusion of ghosts (no photoshop was used, its all on one frame in the camera)
Another way of using light creatively is by having the shutter stay open for a longer duration, and moving the CAMERA around instead of the lights, as the photos of the Christmas trees show.
Get creative, Set the camera to 30 seconds, or bulb if you can, and let the lights create the show you hope for. Remember, tripods are your friend.