Check out this straight forward and simple guide for using NewTek TriCaster M/E's for compositing and green screen work. M/E's are Mix-Effect busses that enable you to create multi-layered productions with ease. TriCaster allows you to use virtual sets as well to add even more pizazz and style to your productions.
Gnuralnet by John Mahoney
NewTek's entire TriCaster line offers very powerful LiveSet functionality, allowing you to place chroma keyed talent into a variety of virtual environments. It mixes powerful video UV mapped video layers with z-layered still images to create a compelling live composite.
I've put together two basic sets that demonstrate this capability. The first set is a simple 'White Infinity' set designed to place talent in front of a white gradient background
The second set I've put together is almost identical to the first set, but allows an image to be substituted on a background layer instead of having the fixed white background.