These four files are scans of a publication called "Science Comes Alive With Reading Rainbow" that provides activities to go with the episodes in the Reading Rainbow television series.




Toys from Trash website has many great ideas for simple ways to investigate science and math
http://www.arvindguptatoys.com/toys.html


Although quite commercial, Steve Spangler's website has some good ideas that do not in every case require purchased materials
http://www.stevespanglerscience.com/experiments/


TOPS -- Teach Science With Simple Things website.
You need to click around on this a bit, but at some point you'll see a list that says "More Sample Labs Available" and there is a list of titles you can download for free. They are also trying to sell the activity idea guides, but there's plenty there for free, too.
http://topscience.org/

Science Kids -- This website has a lot of resources. Be a bit careful about safety. I think this is a site from New Zealand, based on the address, and apparently they allow kids to do things that might not be allowed in U.S. schools any more (e.g., growing bacteria cultures--allowed in high school, maybe). Some of the resources are very useful.
http://www.sciencekids.co.nz/