Thematic maps are very useful when describing statistical data about places. The data, simply, becomes much easier to understand.

Cartographer is a JavaScript library for creating thematic maps on Google Maps which supports custom styling.

It is only a one JavaScript file that relies on the powerful Raphael.js vector-graphics library.

It supports 3 visualizing types:

• Chloropleth (color coded regions)
• Pie charts
• Point clusters

The areas on maps are mentioned as latitudes or regions (depending on the type) which means no hacking or manual calculations.

Every visualization type comes with different options like colors, opacity, stroke & more.

P.S. The library is currently on alpha state but pretty solid.

Mapeed.AddressChooser is a Javascript script for creating an address form with a twist: it displays the address mentioned in Google Maps (can be used with another map provider by creating  your mapping proxy) in real-time.

The script adds a behavior on HTML form, & doesn’t generate HTML markup.

It can also be plugged on any existing forms.

You can focus the map to the user’s city/country with the IP used (if mapping provider supports).

Mapeed.AddressChooser is well documented & has a nice demo with script.aculo.us autocomplete.

Smoot is a tool, developed with xajax and Pear::DB for creating diagrams of icons and links between them.

Features include Google Maps and Google Earth integration, configurable tool palettes, and automated palette generation from a Google local query.

Smoot builds relations between objects with mouse clicks and the result can be stored easily. This nice tool can be a starting or an inspiration point for many projects like "online heritage services", "online diagram services" and much more.