Jupiter is a pleasure to observe in a telescope. On a clear night you can see the stripes in it's atmosphere. If it is facing earth, you can also see the giant red spot. Jupiters red spot is a giant storm that has been visible for hundreds of years.The spot is about three times the size of Earth.
Even through a small telescpoe you can see at leat four of Jupiter's moons, Io, Europa, Ganymeade and Callisto. At times you can view these moons as they pass in from ot Jupiter (a transit). If it is clear enough you can even see the shadows of these moons on the clouds of Jupiters atmosphere.