GRAIL: Gravity Recovery And Interior Laboratory. Two probes are orbiting the Moon in order to draw up an accurate reading of the variations in its gravitational field.
Enjoy Space article - Mission website (NASA)

Launched on 5 August 2011, the Juno probe is to reach Jupiter in August 2016. It will then go into orbit around the gaseous giant and will essentially study its atmosphere and its powerful magnetic field.
Mission website

Launched on 1 October 2010, Chang’E-2 is the second Chinese lunar probe. It is to study our natural satellite from orbit at an altitude of 100 km. It is equipped with several scientific instruments and a camera capable of taking photographs with a 1 m resolution.
Enjoy Space article

Launched on 20 May 2010, the Akatsuki probe was to have reached Venus in December 2010 in order to study its atmosphere and to assess whether or not its volcanism is still active. However, the orbital insertion did not go according to schedule and another attempt cannot be made until the end of 2016 (see this Enjoy Space article).

Official website

Launched on 18 June 2009, the Lunar Reconnaissance Orbiter (LRO) will go into orbit around the Moon at an altitude of 50 km in order to draw up a detailed cartography. The orbiter will also be highly active looking to see whether water is present on our natural satellite in the form of ice, protected in certain craters in the permanently-shadowed regions at the poles.

Enjoy Space article

Official site

En route to Vesta for July 2011.
Official site - Link to image shown below

New Horizons flew by Jupiter in February 2007, enabling its scientific instrumentation to be tested and its trajectory to Pluto to be adjusted. The probe has now gone beyond Saturn’s orbit.
Official site - Link to the image shown below

In scientific orbit. Mission recently given a one year extension by the European Space Agency. Venus Express has made spectacular advances possible in the understanding of this planet’s complex atmospheric mechanisms (notably the presence of a twin vortex at its poles). The probe is also looking for proof of active volcanic activity.
Official site

MRO (Mars Reconnaissance Orbiter) is equipped with several instruments including a camera capable of photographing the surface of Mars from orbit with a 25 cm resolution, which is a first.
Official site - Link to the image shown below

After having passed by the closest planet to the Sun three times, the probe is to begin orbiting Mercury in March 2011.
Enjoy Space News in Brief: third flyby a success
Enjoy Space feature on the initial mission results
Official site - Link to the image shown below

En route to its destination (arrival scheduled for 2014). Successful flyby of asteroid Lutetia on 10 July 2009.
Official site

Active and on extended mission. 30 km travelled over the surface of Mars as of 1st June 2011.
Official site - Link to the image shown below

In scientific orbit since December 2004 and on an extended mission.
Official site - Link to the image shown below

Active - on extended mission.
Official site

On extended mission. 6 and 22 June 2009: Titan flyby (965 and 955 km at closest approach).
6 June flyby on the JPL Site
Official sites: NASA - ESA - ASI
Real time Cassini position (JPL)

On extended mission. After having passed Jupiter and Saturn, the spacecraft is heading towards the limits of the solar system. It is currently 16.46 billion km away from the Sun (which is 110.036 times the mean Earth-Sun distance also known as Astronomical Unit or AU - approx. 150 million km).
Official site

On extended mission. After having crossed Jupiter, Saturn, Uranus and Neptune, the spacecraft is heading towards the outer limits of the solar system. It is currently 13.33 billion km away from the Sun (which is 89.145 times the mean Earth-Sun distance also known as Astronomical Unit or AU - approx. 150 million km).
Official site