Kayak.com helped me find price drops for both of my upcoming trips. I signed up for daily email alerts for 2 or 3 departure/return combos. Every night around 11:00 pm I get my price alert for the day. I knew the typical best price to go for as well as the desired flight times, and was able to jump on it immediately. 12-14 hours later, the price had gone up already. I booked in June for both November and April, the price only dropped lower once, not for my exact dates (weekend flights) but for Tuesday or Wednesday departure and return.

The email alert will also show suggested dates when the prices are lower. The email shows the 4 or 5 carriers with the lowest prices and what those prices are as well as how many stops. Major airlines don't fly direct from my city (unfortunately) so it shows 1 stop prices as well as 2 stops (or more). We do have 2 charter airlines with direct flights, unfortunately it doesn't show those but they're also usually the highest price of course.

Good luck, it can be fun sniffing out a good price!