Here is a clearinghouse of summer research programs throughout the US: The Nucleus!
http://www.cise.columbia.edu/mrsec/index.php
http://www.cise.columbia.edu/nsec/index.php
http://www.ctio.noao.edu/REU (Cerro Tololo Inter-American Observatory in Chile)
The SUNY Oswego Astronomy program in Brazil is HERE
A link to the German Academic Exchange Program's RISE program, which is a summer research program with American undergraduates working with German graduate students on research.