The number is 27!
![20130425_solar-system-missions2013-05_big](https://www.schrankmonster.de/wp-content/uploads/2013/05/20130425_solar-system-missions2013-05_big-500x374.jpg)
Right now there are 27 different missions ongoing to explore our solar system. A high number for something that is not part of our daily news cycle. Those missions currently concentrate on the sun, mars, mercury, venus, the earth moon and some asteriods.
Source: http://www.raumfahrer.net/news/raumfahrt/01052013213936.shtml