http://www.sciencekids.co.nz/gamesactivities.html

Offers a variety of engaging games and animations for learning or review a multitude of elementary science topics.

http://www.fossweb.com/

Foss is an inquiry based learning curriculum, offering this website chock full of activities and lesson plans for use on computers or whiteboards.

http://www.engineeringinteract.org/teachers.htm

I love this site because it not only spells out the standards and objectives covered in each lesson, it also features real world animations and video clips to show student how engineers use science concepts each day in their work. This one is definitely a keeper!

http://www.learningscience.org/

I like this website because it is a place where teacher from anywhere can add resources related to science that are standards based.

http://www.woodlands-junior.kent.sch.uk/revision/Science/

Another comprehensive science game resource.