Attached Link: http://www.thugsatbay.com/tab/?q=zweistein

If you render your animation as seperate screens and save them as png files, they will have alpha channels saved with them, then you can use zwei stein or wax or virtualdub to combine them with your video. Using zwei stein you can make the background a colour and combine the videos like chromakey. Zwei stein is free at the link.