This is a fascinating question! So far, our Earth is the only planet where we are sure that there is life, but the universe is so vast that it seems likely that there are other planets out there that could be suitable for life to flourish. Mars is the only planet in our solar system where conditions are possibly suitable for life, but so far no definite signs of life there have been found. The Mars Rover spacecraft is there right now, analysing rocks and soil, trying to work out if life is present on Mars now, or has been present in the past. If life is discovered on Mars it would be one of the biggest scientific discoveries ever made!
In addition to Mars, some of the moons of Jupiter and Saturn also have conditions that might support life -here is a website about them http://www.wired.com/wiredscience/2009/01/et-life/
Here at Cardiff University,we have a brand new PhD project starting in October, which will be investigating some of these “eco-planets” (planets outside of our solar system) and assessing the possibilities that life may exist there. So, watch this space -there could be some very exciting discoveries coming our way!