May 2008: Land on Mars
Phoenix is the latest
July 2015: Arrival at Pluto
New Horizons is the first mission to Pluto, and our first proper look at it. Next month, New Horizons will also become the latest mission to Jupiter, where it will hopefully do some science and get some pretty pictures. In the long run, New Horizons may also go on to visit other Kuiper Belt Objects.
New Horizons homepage
March 2009: Mars gravity assist
September 2011: Arrival at Vesta
February 2015: Arrival at Ceres
Dawn is a spacecraft I find it easy to get excited about: a mission to Ceres and Vesta, the two largest bodies in the asteroid belt. Vesta seems to be a pretty standard potato as asteroids go, but Ceres is round enough to qualify as a dwarf planet and seems to have some interesting features, although we have no detailed images of it.
June 2007: Venus gravity assist
March 2011: Mercury orbit insertion
The only spacecraft so far to vist the Sun's innermost planet was Mariner 10, probably because not only is it really hard to get to, so far into the Sun's gravity well, but once you're there you have to worry about intense heat and radiation. MESSENGER looks set to give us a good look at a planet that's been off the guest list for too long.