The Committee on International Freedom of Scientists of the American Physical Society is circulating a petition, 

(see http://www.math.rutgers.edu/~lebowitz/HUMAN.RIGHTS/Human.Rights.html, and http://www.math.rutgers.edu/~lebowitz/petition/index.html )

and has also written a letter http://www.math.rutgers.edu/~lebowitz/petition/CIFS_Djordjevic.pdf to BICE protesting Djordjevic' detention. (See also the article in the Pittsburgh Post-Gazette: PittsPostGaz.pdf .)