• National Council for Science and the Environment Internships
• University of Bremen, Research Center of Ocean Margins RCOM
• Marine Environmental Internship Harbor Branch Oceanographic Institute, FL
• Virginia Tech Service Training for Environmental Progress (STEP, water quality)  serves community orgs in VA
• Alaska Conservation Foundation Internships
• National Air and Space Museum Summer Internships
• Resources for the Future Summer Internships in Environmental Policy 
• Geological Society of America Internship Information
•  National Science Foundation's Research Experience for Undergrads.Great listing of summer research projects
•  IRIS Undergraduate Seismological Internship summer research in seismology
• Southern California Earthquake Center summer research in seismology
• National Museum of Natural History Smithsonian Institution Research Training Program
• BRIE Internship program Penn State summer research in biogeochemistry
• Woods Hole summer oceanographic research
• Monterey Bay Aquarium Research Institute
• Oak Ridge National Laboratory:
• Keck Geology Consortium
• MIT Lincoln Laboratory Summer Research Program
• Marine Sciences Research Center, SUNY Stony Brook
• Great Lakes Water Institute Summer Internship
• Department of Energy - Energy Research Undergraduate Laboratory Fellowships
• Virginia Institute of Marine Science Internship Page
• Central American Ecological Internship Programs
• CalTech SURF
• German Academic Exchange Service (DAAD) research internships in science and engineering. hosted by German PhD candidates. must register to see list.

Searchable sites

•  Izzy's jobs - Great page with tons of links to specific jobs and internships in the sciences
• Intern.net - groovy on-line magazine dedicated to environmental internships
•  Rising Star Internships - general
•  Rising Star Internships- Geology Internship Listing
•  Sandia National Labs- profitable listing of research opportunities for both undergrads and postgrads
•  UCLA CARE - Summer Internships - good listing of summer research opportunities and internships
•  InternJobs - large site with listings of jobs, internships and advice
•  Virginia Tech Internship Page and Guidance
•  National Internships Online - National Internships publishes professional internship and part-time employment directories for cities and states in the U.S.
•  Global Routes College Programs - international teaching internships
•  About.com's internship search engine listing
•  Internships in Washington DC - mainly economic, political or think-tank internships
• Envirnomental Careers Organization - includes U.S. Geological Survey and other paid internships for scientists.