In the late 90s, there was an announcement that fossilized microbes were discovered on a martian meteorite that fell to earth. As far as I was aware, it was contested and was the topic of debate for years after in the scientific community.

But, something like that would still count as alien life. Not the kind of alien life everyone fantasizes about, but still something not of this earth.

Maybe now that Mars has been the focus of some of our exploration efforts, something might turn up. There is a Mars lander scheduled in 2018 to conduct geological studies of mars, and another rover scheduled for 2020.

https://www.nasa.gov/mission_pages/mars/missions/index-future.html

SpaceX is also working on their own exploratory Mars missions, but so far I haven't heard of anything that was nailed down quite yet.