You can set up a free account with YAHOO and on your home page there is a section called "Fare Beater". You can click edit, type in your departure and destination city and it will display the best fare and update the fare each time a fare changes. You'll have to click "Book it" to find the details, such as price, restrictions, etc.. You can also sign up with the various airlines for their weekly e-savers, and upcoming fare sales. Another option,go to SmarterLiving.com, click deal alert, they have a slew of information and deals listed.
When I was searching for a flight to Japan to visit my son, I think I got on every deal alert list and there's a ton of them out there. Good luck and happy trails!!