You can use a greenscreen for this. (A plain white sheet of paper works well too!)
Very simple really, using your favorite graphics program (ex. Paintshop Pro or Photoshop), You just extract your subject and place them onto the backdrop of your choice.
I personally don't know how these backdrops will work for video, but I do know that they work very well for still photography.
To see more High quality Digital Backdrops you can visit http://www.nescreation.com
A great source for digital backgrounds / backdrops is located here: http://stores.ebay.com/The-Backdrop-Gallery
You will find high resolution, high quality, and a huge variety of digital backgrounds / backdrops for use with Chromakey screens. These are offered at very affordable prices! Check them out, and also check out comments made by satisfied customers! Can't go wrong here with 100% positives on approximately 2000 items sold!