I'm playing with the location and gmap modules for Drupal 5, and i have to say they're really amazing tools.

This site I'm working on, ThorntonHub.com (very much in beta, it's existence largely just to play with location / gmap) allows lots of map-based interactions without knowing much about the google map api.

You can generate map "views", showing any kind of location based information you want, and you can specify what fields to surface in the preview popup.

Right now, all the site really does is allows users to register, add restaurants in the area, and comment on / rate other restaurants.

Once a user enters a restaurant with an address, location module utilizes google maps to geocode the address, and stores lat/lon coordinates for the node. This allows users to effectively put their pin on the map, without them having to know the lat/lon, and without you having to know how to use google maps to geocode.

Pretty handy i think.

Sadly, they haven't been ported over to drupal 6 yet.