Originally Posted by Calchas

An ExpertFlyer subscription: http://www.expertflyer.com/
The "ExpertFlyer will change the way you fly" tag line (say it in an American accent for maximum amusement) is rather overblown but for me it is well worth 100 USD / year.

EF has access to the airline GDS so it's the same information a travel agent (online or offline) can see.