Map-based Mashups are not new. Overlaying your data on maps are also not new. But serving your Google Earth's Keyhole Markup Language (KML) and its zipped (KMZ) files right off from Amazon S3 is new and innovative.
Few months ago, I blogged about Microsoft's MapCruncher tool that generates requisite tiles/files of your map mashed with Microsoft Virtual Earth and publishes them to Amazon S3 using the "Publish to S3" button in the tool. My Lake Roosevelt and Grand Coulee Dam crunched map is available here.
Likewise, some smart developers utilized Google Earth Network Links to publish files on Amazon S3.
Google Earth has the ability to display data imported from outside sources. Users can create KML, an XML syntax used to create data files, dynamically and overlay the information on Google Earth.
Sam Curren, the creator of ActiveTrails.com, a site that let’s you upload GPS data of your hikes to create trail maps on Google Earth, wrote a nice article - Wicked Fast Google Earth Network Links using KML, Zip files, and Amazon S3. In the article, he nicely explains how he used all these technologies together to create a meaningful app that serves files real fast from the cloud. The article is nice read even though you are not a Google Earth user.
Arc2Earth V2 converts and publishes your ArcGIS data to view in Google Earth, Google Maps or Virtual Earth with a click of a button, right from the app. In the article, they mention what files they publish on Amazon S3 and how.
Of course, my hot favorite is WeoGeo - one-stop marketplace for mapping content. WeoGeo is a killer Ruby on Rails app, built and hosted on Amazon EC2 and uses Amazon S3 to host their KMZ files that you purchase off their website. These high-resolution professional mapping content can be terabytes in size and because Amazon S3 scales as you go, WeoGeo is able to reach to a larger audience while keeping their infrastructure costs down. Do checkout WeoGeo's cool, very intuitive, iPod-style interface, if you haven't already done so.