Need a copy of the Periodic Table?  Another good resource is the Periodic Table of the Elements at the Los Alamos National Laboratory.

For a list of Science related sites, check out the following Dewey Decimal categories:

500 - Natural Science

500 Science
520 Astronomy
530 Physics
540 Chemistry
550 Earth Sciences
560 Paleontology
570 Life sciences
580 Botany
590 Zoology

600 - Applied Science & Technology

610 Medicine
630 Agriculture