all the lines are set by the LVSC (Las Vegas Sports Consultants). its a group of about 5 guys who sit there all day and figure out the lines. it was on sportscenter last year when they had their 5 day series on gambling. as far as i know, these are the only guys who set the lines, and then from there the movements for each individual book change based on the money coming in.
edit: after getting more info, LVSC was founded by Roxborough. they are contracted out by the books to set the lines independently.
http://www.lvsc.com/index2.html
google cache of about.com article