Recently, the announcement of a European exoplanet search discovering over thirty new planets orbiting stellar systems other than our own caused much sensation. Using extremely precise instruments capable of determing minute rotational "wobbles" in distant stars, the managed to find exoplanets much smaller, and hopefully rocky like the Earth, than the gas giant planets first found with this method.
This makes more than 400 known exoplanets. Just twenty years ago it was pure science fiction that we could detect actual planets around distant stars, stars whose brightness overwhelms anything orbiting around it (unless it is a twin-star system!).
Just the other day NASA researchers announced their discovery of organic molecules in the atmosphere of a gas planet, the second such planet they have found. That makes two planets outside of our solar system in which the basic chemical ingrediants of life have been detected, water, methane and carbon dioxide. That may not sound like much but being able to detect these chemical pattersn should one day help us accurately detect smaller, earth-like exoplanets.
For a Flash animated timeline of humanity's history of planet and then exoplanet hunting check THIS from NASA. Good stuff.