From Denny: NBC's The Today Show did this interesting segment about UFO's. Of course, it covers from the whacky cultural fun to the serious endeavors as documented by world governments.
As a kid growing up in the intelligence community I remember all the adults talking about this subject endlessly: what they had heard from pilots' eye witness accounts - as well as the mathematicians and scientists speculating as to the percentages of other intelligent life. I guess at some point in human history we will have to deal with the meeting of alien species.
Of course, if you take a look at ancient cave drawings, Egyptian hieroglyphs and the mountain top airstrip like earth drawings in Peru it does give you pause, wondering if humanity has already met and friended people from other worlds.
Rest assured, the SETI project set up by co-founder of Microsoft, is still listening to the universe for signs that company might be coming...