Mars
Regarding costs, missions, challenges...search yahoo.com or google.com or YouTube.com for "Mars" or "Mars and colonization" or similar terms.
Mars Prizes
http://www.youtube.com/watch?v=w7lG36KSeaQ
Robert Zubrin on Colonizing Mars
http://www.youtube.com/watch?v=T5uImXbhQM8&feature=related
http://www.youtube.com/watch?v=9hQ5qXVgmHI&feature=related
Getting People to Mars
http://www.youtube.com/watch?v=Mm34Muv6Lsg&feature=related
Science Agogo Article:
http://www.scienceagogo.com/news/20100919182931data_trunc_sys.shtml
Other ideas: