Here is a list of summer undergrad/first year grad astronomy internships I'd suggest.
I've included a few contacts.

NASA Goddard Space Flight Center (GSFC)
Catholic U of America (a second way to work at GSFC) - contact Dr. Fred Bruhweiler at CUA Physics
NASA Ames
NASA Johnson
Jet Propulsion Lab
Lunar & Planetary Laboratory
National Optical Astronomy Observatories (both Kitt Peak and Cerro Tololo) www.noao.edu
Gemini Observatory www.gemini.edu
National Solar Observatory www.nso.edu
Space Telescope Science Institute www.stsci.edu
Arecibo Radio Observatory (Puerto Rico)
National Radio Astronomy Observatory (3 sites: Charlottesville VA, Green Bank WV, Socorro NM)
Center for Astrophysics (based at Harvard)
Naval Research Lab (Washington DC)
McDonald Observatory (Texas) http://www.as.utexas.edu/reu/
Maria Mitchell Observatory (Nantucket)
Lowell Observatory www.lowell.edu

worth trying:
Fermilab
Joint Institute for Laboratory Astrophysics (Colorado)
Southwest Research Institute

any university with a big astronomy department/program, including but not limited to
Wyoming Infrared Observatory
Cornell (runs Arecibo)
*Univ. Toledo
*Univ. California at San Diego (UCSD)
*Univ. Wisconsin
etc.

* had UL summer student:
2006 Chip Davis, Univ. Toledo
2006 Wes Miller, UCSD
2007 Blakesley Burkhart, Univ. Wisconsin