Ebrahim Hamidi is facing execution in Iran for false accusations of homosexual assault brought against him when he was 16 years old.  His accuser has since recanted, but Iranian officials are still planning to execute Ebrahim on the basis of confessions he made after allegedly being tortured.  You can sign this petition on Ebrahim's behalf: 
http://www.gopetition.com/petition/38289.html

A more detailed version of Ebrahim's story...  
http://www.guardian.co.uk/world/2010/aug/08/iran-mohammad-mostafaei-rights-lawyer