Hi - just wanted to let you all know that the new RealitySets.com (not my company) just released their Volume 4 of video backgrounds for chromakey shoots.
I ordered mine when it first came out a couple of days ago, I've bought all his sets because they're "the next best thing to doing your own on-location shoots" for video backgrounds for virtual sets etc, worth taking a look at.
Workflow: I usually key my footage in Serious Magic/Adbe Ultra, then overlay it on one of these clips in Vegas.
-ken