Interactive Website with many Science Activities -

http://www.dlese.org/library/index.jsp - This digital library of Earth Science has an abundance of information.

http://www.bbc.co.uk/schools/scienceclips/ages/10_11/forces_action.shtml

http://www.brainpop.com/

http://yucky.kids.discovery.com/

National Zoo - http://nationalzoo.si.edu/Animals/default.cfm - you can even see some animals live via web cams.