Short Words to Explain Relativity
http://www.muppetlabs.com/~breadbox/txt/al.html Relativity is explained in words of no more than four letters.
http://www.keveney.com/Engines.html This is both fun and educational. You can see how all kinds of engines really work.
The T.W.I.N.K.I.E.S. Project
http://www.twinkiesproject.com Scientific things you can do with America's snack food with a shelf life of years, such as gravitational response tests, radiation tests, and Turing tests.
Welcome to Heavens-Above!
http://www.heavens-above.com For stargazers, this website gives you times and locations to spot all kinds of satellites, the International Space Station, comets, planets, and constellations.
http://www.ginakamentsky.com/workpg1.html Gina Kamentsky's handmade mechanical banks.
Ig® Nobel prizes
http://www.improb.com/ig/ig-top.html The official website of the Ig Nobel Prizes, sponsored by the Annals of Improbable Research (AIR).
http://hubblesite.org/newscenter Enjoy the site and see why the Hubble Space Telescope must be saved.
HowStuffWorksLearn How Everything Works!
http://www.howstuffworks.com Just what it says: how everything works, from snowflakes to TiVo to handcuffs to building muscle mass.
PatentsPatent Full-Text and Full-Page Image Databases
http://www.uspto.gov/patft/index.html You can look up every U.S. patent ever issued.
The Buckminster Fuller Institute
http://www.bfi.org Look at this and be inspired by Buckminster Fuller and his ideas.