http://www.thefreedictionary.com/behalf says: " A traditional rule holds that in behalf of and on behalf of have distinct meanings. In behalf of means "for the benefit of," as in We raised money in behalf of the earthquake victims. On behalf of means "as the agent of, on the part of," as in The guardian signed the contract on behalf of the minor child. The two meanings are quite close, however, and the phrases are often used interchangeably, even by reputable writers."

i have to agree with peachy, i cant remember the last time I heared someone say 'In behalf of here in England either, it sounds a little strange to me!'

"On behalf of" means the person performing the action is acting as a representative of another person or group. "On behalf of the students, I would like to thank you for your presentation." ...I remember this exact phrase heard so many times at school. :) "I'm calling on behalf of Mr Edgmont" ...you are obviously not Mr Edgmont, but you are calling in his place to do his business. "In behalf of" is very rarely used here in Australia; we would simply use "for the benefit of" instead.