A few discoveries of the Hubble Space Telescope :

1) The Hubble Space Telescope found the 4 moons of the dwarf planet Pluto. 

2)Has found a distant Supernova that suggests that the Universe only recently began speeding up. 

3)Detected the first organic molecule that was outside of our solar system. 

4)Helped scientifics find how planets are born.  
source:
 http/:www.nasa.gov/mission_pages/hubble/mail/index.html