Here are some summer research opportunities in the US (and one in Hong Kong) that fund non-US citizens.
Research in Industrial Projects for Students (RIPS) 2011 at UCLA (Also has a program in HongKong)
http://www.ipam.ucla.edu/rips/
http://math.williams.edu/small/application-information/ (their website says they have funded non-US students in the past)
NIMBios 2011 Summer Program National Institute for Mathematical and Biological Synthesis (NIMBioS) at the University of Tennessee, Knoxville http://nimbios.org/education/reu2011
DIMACS REU DIMACS/DIMATIA REU CCICADA REU Rutgers Math Department REU (foreign students enrolled at a U.S. university are eligible under the CCICADA program) http://www.dimacs.rutgers.edu/REU/2011/announcement.html
Mathematical and Theoretical Biology Institute MTBI Summer Research Program http://mtbi.asu.edu/SummerProgram.html