USAPhotoMaps is one of the coolest pieces of (free!) software I’ve ever seen. It uses images from the MicroSoft TerraServer to populate location information with satellite photos or topographical maps. It interfaces with several GPS systems (such as Garmin or anything that groks NMEA) and will show your current location, let you send/receive waypoint data to/from the GPS unit, zoom in/out, scroll, create routes to send to your GPS unit and lots of other things. This thing has it all and it’s free! If you’re into maps or GPS (you don’t have to have a GPS unit to use it), this is a nice thing to have.