NASA Homepage - This site contains information about NASA Space Center as well as general student information about the planets and space exploration.
http://www.nasa.gov/
The Why Files: Science Behind the News - This site explains the science behind some of the current events in the news.
http://whyfiles.org
PubMed and Medline - This website is a database of information on the life sciences. It would be a good resource for those in science courses.
http://www.ncbi.nlm.nih.gov/PubMed/