if your travel plans are somewhat flexible -- also look at what the difference would be if you flew out on a weekend - or did a saturday night stay -- a lot of times it will be a little cheaper to come back on sunday (because not many people travel on sundays)
Also don't over look going directly to the airline sites.. like
www.aa.com, or
www.united.com or even
www.aircanada.com -- they will often have specials advertised on the websites ...(and make sure you sign up for frequent flyer miles if you don't have them already - being a 'member' also will often get you more specials that are advertised for members only.)