We are finding new planets in other solar systems all the time. Some of them are in a habitable zone of their sun. Are we able to detect the atmosphere of any exoplanet? Is there any atmospheric element that would be indicative of known life forms?
Yes, they are starting to examine exoplanet atmospheres. A spectroscopic analysis is made of the light from a exoplanet transiting its star. The spectra of the star is subtracted from the combined star/planet data, and the remainder is assumed to be the absorption spectra from light passing through the planet's atmosphere. Here's an article from a recent Centauri Dreams column that goes into some detail: Tau Boötis b: A ’3-D’ Look at Star and Planet.
As far as elements indicative of life forms, one would expect to see water, carbon dioxide and methane on a life-bearing planet, but, of course, these are common substances that can readily be explained by natural processes.