Here it is:
http://www.ktel-chalkidikis.gr/index.php?act=viewCat&catId=1019
Afitos or Athitos is the same.
Remember that to go to Sithonia peninsula, you must change buses at Nea Moudania town. So, check the time of arrival to Nea Moudania from Afitos, then from Nea Moudania to your destination in Sithonia or Athos.
http://maps.google.com/maps?saddr=%CE%86%CE%B3%CE%BD%CF%89%CF%83%CF%84%CE%BF%CF%82+%CE%B4%CF%81%CF%8C%CE%BC%CE%BF%CF%82&daddr=%CE%9D%CE%AD%CF%89%CE%BD+%CE%9C%CE%BF%CF%85%CE%B4%CE%B1%CE%BD%CE%B9%CF%8E%CE%BD-%CE%9D%CE%AD%CE%B1%CF%82+%CE%A6%CF%8E%CE%BA%CE%B1%CE%B9%CE%B1%CF%82+to:%CE%A0%CE%B5%CF%81%CE%B9%CE%BC%CE%B5%CF%84%CF%81%CE%B9%CE%BA%CE%AE+%CE%A3%CE%B9%CE%B8%CF%89%CE%BD%CE%AF%CE%B1%CF%82&hl=el&ie=UTF8&ll=40.122191,23.575287&spn=0.44735,0.877533&sll=39.993956,23.922729&sspn=0.224096,0.438766&geocode=FTDiYwIdCo9lAQ%3BFcwCZgIdwo1jAQ%3BFSjYYQIdKBltAQ&vpsrc=6&mra=mi&mrsp=2&sz=11&t=h&z=10
As of prices, they vary from EUR 3 to 9, one way.