I like Amber's suggestion - so far that's been the only thing that's worked for me
Actually not even that - I completely and totally clam up in front of people (with singing, I have not problem with public speaking etc) but singing? I just can't do it
I was in a band (the drummer) and we did The Apartment Song - it was great during practice - but when we'd perform I'd totally chicken out and no one could here me...it really used to tick off our lead singer