If you have an iPhone or an iTunes account, check out the "Official Plates" app.  It basically allows you to look up diplomatic license plates assigned by the US State Department.  It's an easy to use app and designed for people like me who actually need it for my job on a daily basis.  I work in an environment where knowing this information at the blink of an eye is VERY useful.  It also has Federal US Government tag codes as well (GSA, etc).