Mashups can be defined as "a website or web application that seamlessly combines content from more than one source into an integrated experience". Marshups are an excellent example of the increasing variety of things search engines can do and what you can do with search engines and the different kind of experiences provided by Web 2.0.
For example by means of Google and Yahoo APIs, a broad range of data that was coded as to an exact geograhic location was integrated with maps and aerial images.
Check out:
ws1.inf.scd.yahoo.com/maps/applications.html
www.googlemapmania.blogspot.com