Hi Jay
The programme I use is called Ultra 2 from what was Serious Magic - sadly now part of Adobe and sold as part of the CS3 Suite
The green screen itself is a proper 10ft x 24ft chromakey backdrop which I have since bought some Strand Iris 1 cyclorama floodlights to light the backdrop with from above and slightly in front.
You take your footage into Ultra and key it in there.
You then render out the finished avi or other file format you want to use and place it into your edit programme in the way you would any other video clip for editing.