Didnt expect this to trend on HN. I used to travel every week for work and learned to used this and fly.faa.gov/ois to find out how long ground stops will be during delays for years.
While I'm on this soapbox: ExpertFlyer. If you travel once per month or more, it is ABSOLUTELY worth the $10/mo. They provide a lot of info straight from GDSes, somehow. Invaluable for rebooking and seat changes.