FLIGHT STATS - across the country - Check Your Airports for Delays at a glance- then get details

You'll want to book mark this one:

The status information provided on this site indicates general airport conditions; it is not flight-specific. Check with your airlineto determine if your flight is affected.Information on wait times at security checkpoints.

http://www.flightstats.com/go/Airport/currentAirportDelays.do?region=usFAA