The European Extremely Large Telescope (ESO)

This will, by far, be the largest optical telescope in the world. Capable of detecting Earth-sized planets around other stars, imaging Jupiter sized extrasolar planets, examining the early universe and so much more, this is the telescope of the future. Check out the video above and the link below for more information.

There's a great writeup on UniverseToday.com here: http://www.universetoday.com/2010/02/12/armazones-chile-to-be-the-site-for-the-42-meter-european-extremely-large-telescope/