Those of you who use Firefox
And you should be! There's a new extension available called Fare Compare According to the d/l page: Easily monitor the lowest fares from your selected airport. Fares are updated as soon as new fares are released by the airlines (three times per day on weekdays and once per day on weekends). The application currently supports fares for US and Canada. International fares are in alpha testing and should be released later this month. Could prove useful for getting the best possible fare.