I need a JavaScript programmer for mapping project

Javascript Programmer required.

To create an interactive map with Google Maps api to place markers of various categories placed on a map in different colours.
Data for the categories and marker locations will be available from a JSON API feed.

We are looking for something similar to this to be created http://www.sailscotland.co.uk/sail?boatyards=boatyards&charters=charters&region=Argyll%20and%20the%20Islands

Marker locations should be loaded from JSON and placed on the map without post back, unlike this example.

Finished article does not need to be within any HTML template, just the working mapping section needs to be completed for this work.