Bits of code that you may be able to adapt for your purposes.

PHP

• Conditional Geo Mashup Map Template Code
• Geocode Gravity Forms Fields
• Global Map Of The Current Category
• Hide posts based on a custom field value
• Load A Javascript Library (MarkerWithLabel) In A Geo Mashup Map Frame Template
• Map Centered On Current Post
• Plugin To Add Map Automatically To Posts
• Post Query Contextual Map

Javascript

• Custom Markers
• Google custom styles
• Load KML Attachments For All Geo Mashup Map Markers
• Markers as links