Space.com has a good article on Gliese 581 C, a planet that seems to be at the right temperature for liquid water to exist on the surface. I'm surprised that there isn't more interest and more research funding going into this. Even if it took centuries or thousands of years, the possibility of mankind stepping off our little rock strikes me as extremely exciting. If the planet is covered by water and is the right temperature, it doesn't seem like it would be too difficult for humans to live there and terra-farming (if plant life doesn't already exist there) should be pretty easy to do over long periods of time. In the short term, it even seems possible for humans to set up giant plastic domes where they could live and farm.
A excellent blog discussion of the new planet can be found at Centauri Dreams.