Google continues to provide a wealth of useful easy-to-use tools that can be used well in the classroom. Some of these are newer and some have been around for a while. All of these tools, as well as additional tools can be found at Google Options.
Another great tool for collaborative projects. Takes the power of Google Earth and focuses on an easy to use interface for incorporating varying content.
Blogger.com can easily be incorporated into the classroom (and outside the classroom for that matter). Students can post comments, photos, videos, etc.