The last thing any real estate agent wants to do is spend time entering listing data into multiple systems. From a search engine perspective, the last thing a real estate agent should do with their website is to wrap their MLS listings inside an 'iFrame.'
We effectively solved both problems by implementing a custom Drupal-powered site with an RETS integration. This means that the listing data is automatically pulled into the site every night. My client enters their information once into the MLS system and the website reflects those changes the very next day. It even pulls in photos and generates an embedded map based on the property's coordinates.
Best of all, each and every property listed on the site gets indexed by search engines, which greatly increase the chance of potential clients actually finding the site.