The Drake Equation is the equation formulated by Frank Drake.  It is a speculative equation that is used to attempt to estimate the number of civilizations alive and kicking in the galaxy today.  It is stated as such.

N = R* × f_p × n_e × f_l × f_i × f_c × L

So why are you bringing this up Greg?  Well I'm glad you asked.  Astronomers have been using highly specialized techniques lately to detect planets around nearby stars, in general by detecting the wobble in the star's path caused by massive close orbiting planets. 

So historically we have been able to Estimate R*, which is the estimate of the number of stars in the Milky Way Galaxy. 

And recently, with our new capabilities, we have been learning about how our estimates play out with f_p, which is the estimate for the fraction of the stars that have planets around them.

But the rest of the variables have been wild ass guesses.

Now Astronomers have spotted a potential n_e data point.  n_e is the number of planets per star that might sustain life. [linky] They believe they have spotted a candidate planet.  Now this in its own right doesn't tell us much.  What it does reveal is the growing capability of astronomers to detect smaller and smaller planets.

"On the treasure map of the universe, one would be tempted to mark this planet with an X," Delfosse said.

As the technologies and skill of the astronomers continue to increase, we may very well nail down the front end of the Drake equation.  We may statistically "know" three of the seven variables.

If we can refine our techniques and increase the power of our telescopes even further we might be able to answer f_l which is the fraction of planets where life evolves.  Spectroscopic analysis comes to mind.

With knowledge of four of the seven Drake equation variables we will have a much better grasp of our standing in the universe.

Beyond that we really need a way to communicate with the intelligent life supposed in f_i and f_c.  But still...

Update: Let's hear what Carl Sagan has to say about it: