NASA and NSF encourage students to apply for their paid summer research positions:
NASA offers paid undergraduate and graduate level internships in a wide variety of disciplines. Over 200 internships are available. The deadline is March 1st, but offers may begin going out as early as Feb. 2nd.
Visit http://intern.nasa.gov to apply for up to 15 opportunities with a single application.
NSF offers a wide variety of paid summer research experiences for undergraduates. To search over 600 programs, please visit: http://www.pathwaystoscience.org/undergrads.asp
NSF For mentoring and professional development support funded by NSF, please take a look at AGEP alliances: http://www.agep.us