Below is a list I put together for our undergraduate students who are searching for internships (Please note that this is by no means an official or complete list, and it doesn’t mean our program has an agreement with any of them). I would also recommend going through the websites of local companies.
Best of luck.
DOE internships: http://humancapital.doe.gov/jobs/internships.htm
Federal Internships: http://www.makingthedifference.org/federalinternships/directory
NASA Undergrad Student Research Program: http://usrp.usra.edu/