Below are some websites with links to activities for scientific outreach at the elementary and middle school levels.
Science is Fun, Shakashiri lab
Adult Role Models in Science list, UW-Madison Institute for Biology Education
Science Buddies – lots of activities in different disciplines
UW-Madison Biology Outreach club, list of activities (contact BOC for details at firstname.lastname@example.org
NOVA ‘Making Stuff’ Materials Science Activities
UW-Madison Materials Research Science and Engineering (MRSEC) website.
* MRSEC also has training videos for many of their outreach activities.