Choose "Advanced Search," then select (click on) "Applicant Type" and choose "Undergraduate" or "Graduate Student." Select "Keywords" and either select "Science and Technology" or specific topic. More advanced searching is possible; play around. Remember to "Clear Search" every time, or the blanks will automatically refill.
National Institute of Standards and Technology, Gaithersburg Campus
Harvard Smithsonian-Center for Astrophysics
National Science Foundation Research Experience for Undergrads at various national universities including Drexel University, University of Houston, Baylor University, University of Toledo, Maria Mitchell Observatory, College of William and Mary
Carnegie Institute of Washington, Department of Terrestrial Magnetism