Almost all of our knowledge and good images of the outer planets are due to the Pioneer and Voyager spacecraft of the 1970's. New Horizons, launched in 2006, will be the first probe that I know of since then to go out that way, so we will likely finally get some new knowledge and pictures. It will also be the first to visit Pluto, which should be interesting because the best picture we have of Pluto is just a pixelated blur.