There isn't any conclusive evidence yet. Although, it seems somewhat rididiculous that there aren't ant existing alien life forms. The odds are incredibly for there being some form of life out there. They most likely won't be inteligent creatures who are millions of years ahead of us in technology, probably either simple "animals" or bacteria.
Almost a decade ago, there was a sample of rock found that wasn't from earth. And inside that rock were traces of extinct bacteria that had never before been catalogued on earth.
Add that with the recent discovery that Mars could still have flowing water even today, and you've got strong evidence for other life. Chances are, we won't find it in our backyard in this solar system, or even in the next star, but we could find some if we venture farther.