The Butterfly Site is worth checking out.
McGraw-Hill Encyclopedia of Science and Technology has a companion website.
Live Science - A huge variety of articles and information.
The Periodic Table of Elements is offered in a "clickable" format at this site.
Confused by computer jargon? Data Powers of Ten will help you to picture that "byte!"Interested in Insects? This site is searchable and very informative!
Or, try 3DInsects!