Nope. It would probably have been the news of the decade if they had. It's speculated that a few of their moons might have micro-organisms- especially Europa, one of Jupiter's moons, because it has an ocean under its ice surface- but we won't know until a probe is landed and samples are taken.
I think I remember hearing something long ago about one of Saturns' moons having plant life.
If you think that's crazy, you should check out Io (another moon of Jupiter), which is covered in active volcanoes.
They were probably speculating about life on Saturn's largest moon, Titan. It has a really thick atmosphere (which could theoretically keep it a bit warm), so no one knew back then what was beneath it. They landed a probe a few years ago, but didn't find any life.
As already said, "alien" just means foreign.
It's unlikely there's any water vapour to speak of on Io. It doesn't have an atmosphere and it's practically devoid of water.
That would be the Drake equation. As any good statistician will tell you, it's the more samples you have, the more accurate your results are. We'd need to sample many planets with and without life on them to come up with some decent numbers for the variables. With current technology it's much harder to find potentially inhabitable worlds than gas giants, so at present it's impossible to figure out the different variables. Also, some people (such as myself) think the equation is wrong anyway.
