Create map that show user Location and last user's post
Once I had to do the very same thing and followed this good video by Drupal Therapy. It uses GMap (API 2) + Location modules instead of Open Layers, but if you're on D6 this is still a good solution. If you enable user-locations and node-locations functionalities in the modules page, you'll find predefined Gmap user/nodes location views. If you need to associate geographic information only on certain content types (and not to all nodes), you'd better enable location-CCK and just add and configure a location field to your desired content type, then create your Gmap view.

Hope it helps you to start with maps in Drupal.