On the NETTUTS website today there's a new tutorial about mashups - specifically showing how to create a sample one by combining three services: Google Maps, the IPloc service and the Beer Mapping Project.
This tutorial will show you how to create a mashup of three different APIs including integration with Google Maps. This idea came about when I was searching through ProgrammableWeb's API directory for a couple APIs that complimented each other enough that I could use one to provide the other with data. What I came up with will be known as the "Beer Mashup".
They include links to scripts to interface easily with the APIs and the sample code you'll need to query against them. They wrap it up with the HTML for the output page (a map showing "beer hot spots" near your area) and the download of the source and demo to give an example of how it should look.