Hi Sarah,
There are billions of stars in our galaxy, and some of them are bound to have planets similar to the ones in our solar system. I'd like to think that it is possible that life has developed elsewhere in the universe. However, life on other planets is probably very different from life on our own planet.
Many scientists are hoping to find evidence that life once existed on Mars. Some people think that there may even be a chance that there is life deep under the ice of Jupiter's moon Europa. There are also scientists who are listening to radio signals from space for signs of intelligent life. Unfortunately, space is very big, so I think it is unlikely we will find evidence of intelligent life during our lifetimes. Then again, you never know! Some of the greatest scientific discoveries have been made when people least expected them.
If you would like to learn more about the search for extra-terrestrial life in our solar system, check out the NASA Astrobiology Institute: http://astrobiology.arc.nasa.gov/
To learn about the search for intelligent life in the universe: http://www.seti.org
Kris