Before you leave for the airport, check the FAA's Air Traffic Control System Command Center. Click on any of the major cities, and you'll see what delays they are currently experiencing. Includes weather and congestion delays.
This site from The Weather Channel allows you to view flight arrivals by airline or city. Each listing will tell you the amount of flight time remaining.
Easily locate delays with FlightStats. Find cities easily using a map as well as other helpful tools.