The following job posting sites provide some resources for searching for jobs in a variety of science fields. Remember, though, that job posting sites such as these are only one way to search for a science-related job. Make an appointment to meet with a career advisor so that you can develop a comprehensive career search plan, including targeting specific employers, searching for job openings, and networking.
Spotlight on Careers has a wealth of information about careers in the sciences, including links to job and internship databases.