Most my portrait shots done "In Studio" are photographed in front of my 30'x20' green screen. Using the latest in PS software plug-ins, the ability to place my subjects on any background I (or they) chose is virtually unlimited. I have spent months perfecting the technique and I can honestly say I prefer this method to the standard muslin backdrop shots.
My other shots are standard, non-chromakey compositions.
CAMERA: Canon T3i
PRIMARY SOFTWARE: Photoshop CS5 / Primatte / Ultra Key
NOTE: If anyone is interested in learning more about chromakey photography, drop me a note and I'll be glad to answer any questions.