Our clients 5k50 have recently opened a preview of their real-estate search system which is based on Apache SOLR and Maptimize. Maptimize is a very nice tool which which manages the display of data on Google Maps by merging markers which are geographically close together.
We initially audited the existing SOLR setup then redesigned it to add more functionalities and optimise the search speed. The search itself is an interesting mix of map-driven filtering with SOLR queries and faceting. Any changes to the map (click on a cluster, zoom in/out) are reflected in the search results and facets and vice-versa.
Navia is a nice showcase for some of the most commonly used features of SOLR (i.e. faceting, more-like-this, autocompletion) and has a great identity thanks to its mix of geo and text search. It is currently in beta mode so we can expect a few more improvements over the next few weeks.
And please feel free to give it a try so that we can get plenty of data on the performance :-)