America's Career Information Net -- Find occupational requirements and other information on careers. [Click on "What it takes!" tab]
Bureau of Labor and Statistics Career Information -- "Jobs for kids who like science." Mainly, pharmacist, chemist, doctor, nurse, pilot, and computer repair. For each category be sure to click on "Similar Jobs."
Career Zone -- Click on blue circles for such categories as "Engineering and Technologies," "Health Services," and "Natural and Agricultural Sciences."
Life Sciences -- Careers in biology with some links to other life sciences.
Occupational Outlook Handbook, 2002-2003 published by United States Department of Labor [You can search by keyword, job category, or alpha listing of job title]
The Princeton Review: Careers -- Investigate careers, to learn more about the professional opportunities that appeal to you.