Here are a few more good general science sites:
National Science Foundation
http://www.nsf.gov/
NASA
http://nasascience.nasa.gov/
Science Friday
http://www.sciencefriday.com/
Proceedings of the National Academy of Sciences of the United States of America
http://www.pnas.org/
I would recommend staying away from single-issue sites. All too often they're pushing their own agendas.