Videos of 384 demonstrations performed by teachers. Each one has a write up to replicate the demo from.
http://www.nku.edu/~sieveb1/demos/
A demo resource site with many videos and some instructions for and discussions of demos.
http://www.abc.net.au/science/surfingscientist/
An arrangement of demos, lesson plans and videos spanning multiple science fields geared mostly to elementary students.
http://www.stevespanglerscience.com/experiments
A plethora of science experiments over a range of topics. The site also has science kits, supplies and gadgets for sale.
This site has a group of experiments that can be done at home using household materials, descriptions of some common and interesting chemicals, and many additional resources.