Scirus
Scirus is the most comprehensive science-specific search engine on the Internet. Driven by the latest search engine technology, scirus searches over 200 million science-specific Web pages.

YES Mag: Canada's Science Magazine for Kids
Interesting site based on the publication of the same name.

How stuff works.com
What makes it tick? Find out here.

Science Net 
Toronto Public Library's interactive science site for students and teachers. Includes grade specific websites.

Discovery Channel Canada

Ontario Science Centre Online