John:
Just to clarify, we live in a day when MLS data is shared all over the place when it is entered into the MLS. This process as known as "syndication", similar to what we have done for years in the newspaper business. The problem at this time is that although there are mechanisms to push out new listings to all these sites, most of them never update old data. For this reason, the MLS is the only true and accurate sourch of information on properties for sale. As the others here have suggested, ask a REALTOR(R) to set up automated searches for you to make sure you are getting the data you need in real time.
My $0.02,
Steve
P.S. or set up searches on my website at the link below... - Fri Sep 11 2009, 10:53