Clustered Google Map
The best way (the Drupal way) is to build on top of available Drupal features, rather than creating a custom solution that may do the narrow task at hand, but bypasses a lot of the built-in structure that carries a lot of value when using Drupal. 

Views module is used to build the page you linked to, and Views is also the best module to use to list the geo-data to be displayed on a map. 

Each node from that table has Longitude and Latitude coordinates (visible when you visit a node page, not directly in the table). These coordinates fields can be used to feed a Views map display. 

You'll need to install a module that provides a special Views Format that renders a map. Then add that Display type to the same Views where the page you linked is built. Adjust the fields (override) to provide for the map display. 

Are your Longitude/Latitude fields from Geolocation Field? Check under Structure > Content types > SAR Saves > Manage fields. Also check under Extend which geo-modules you have available. 

With Geolocation Field you already have everything you need, you just need to configure a new map display in Views configuration, no coding required ;)