As much as I would Absolutely LOVE to believe that flying saucers,'s or little green men exist, I have to say that I just don't really believe they do...
There are a lot of people who would disagree, but I'm sorry, there just isn't any real evidence, proof or even anything anywhere close to it... There are a lot of rumors that don't hold water, a lot of people have created hoaxes (some pretty elaborate) and some of the best movies ever made have been based on aliens coming to earth.
The biggest case for there not having been aliens visiting earth are the distances they would have to travel to get here. We are nowhere near being able to travel at the speed of light (and according to Einstein it's totally impossible to do so) but assuming it WERE possible - unless there were aliens anywhere near us, it would take hundreds - even thousands of years for them to get here (and who would want to sit in a tiny little ship for hundreds or thousands of years just to visit THIS planet???)
No, I don't believe in UFO's - but I sure do hope I'm wrong!!! (unless they really ARE human eating lizards that just want to use us as a food source...)