Current unmanned missions:
This diagram, made by Olaf Frohn, comes from his blog, Armchair Astronautics. He keeps an updated list of all current probes (one of the best updated sites). The planetary Society uses the same diagram at this page: What’s Up in the Solar System.
My list of unmanned missions may not cover all past or current probes but the ones I find interesting. Other list of missions:
The Planetary Society – Space Missions
Encyclopedia Astronautica – Manned spaceflight
Practical Space – Solar system and spacecrafts
Outer Places (Nice infographic!)
My own results: