If you are interested in shooting scenes using chromakey (also known as greenscreen, bluescreen or bluebox), here is an interesting blog that discusses shooting chromakey for post production.
At the 2006 VidExpo this fall, a graphic artist from a Denver television station discussed shooting greenscreen for post production.
Many of us think of using an external box or video switcher to create greenscreen effects in real time. And while this may be the way to go when you are shooting a weatherperson in front of a map, it's not always the best way to go.
You can make some fascinating composite video clips by using the greenscreen capabilities of Final Cut Pro, or even something as simple as an Avio or Casablanca editing appliance.
Take a look at the linked article and see if you can stretch your imagination when keying in your next project.