The google holodeck is used by google engineers to test the usability of StreetView photos. It's also a pretty cool tool to use, if you happen to be at the Google I/O conference in San Francisco this year.
Google's version of a holodeck is a small room that is equipped with flat panel television displays turned 90 degrees. You stand in the middle and can see an almost completely circular view, based on the Google Street cam pictures available for that location.
via Google Holodeck Now Operational: Science Fiction in the News.