One of the dealers I work for just sold one of these for an upcoming job - [Link: wyrestorm.com]. I haven't seen it in action yet, so I don't know if it performs as advertised, or not. The price is definitely right :-)

Crestron also recently released a new model ([Link: crestron.com]) which is a replacement for their DVPHD which has been around forever and my personal favorite.

Also check out RGB Spectrum, and possibly Atlona (I think they have one, but could be mistaken). Other than that, try searching for "multi-window video processor".