NASA PlanetQuest is a very interesting site from NASA that has links and resources about NASA's search for new planets outside of our solar system. There are multimedia resources, links, videos, photos, news, blogs from scientists, and much more.
The site also has six very cool interactives that would be great in the classroom: Extreme Planet Makeover (create your own planet), PlanetQuest timeline (history of exoplanet speculation and exploration), Alien Safari (learn about bizarre and extreme organisms found on Earth), Interstellar Trip Planner (plan a trip to outer space), Alien Fact or Fiction quiz, and 3D Guide to the Galaxy, which lets you explore our galaxy in 3D. These are fun and educational and can be used in a variety of classrooms as projects.
There is also a page on Education that includes more resources and links to learn more about space exploration and the search for planets.
This is another excellent resource from NASA.
Check it out: http://planetquest.jpl.nasa.gov/
NASA Speakers Bureau
NASA - Find lots of great educational resources from NASA here