Learn about your airplane seat before you buy it.
World wide train information. Learn about train classes and equipment.
Bus companies all over the world.
Invaluable website that allows you to scan for the cheapest fare. NOT like Orbitz etc.. It allows you to put in where you are and it will show the cheapest tickets to anywhere.
Airfarewatchdog give you daily emails about the cheapest fares to anywhere from where you are.
Shows which airlines service which airports
Find parking near airports that''s much cheaper.
Query google about weather and flights from your phone.
Avoid airline delays.
Shows flights and ratings by users for various aspects like aircraft
Interactive map of Paris
All bus schedules for Mexico
Very active travel forums with zero tolerance policy to spammers. - highly recommended although not active anymore.
Very active forums relating to commercial flying. Mileage runs
Announcements about airline route changes
Site to compare the new cheap buses between cities in the eastern US. As bus services open up in other areas they'll probably cover that too.
Prediction of flight delays
Another travel aggregator but includes Amtrak which is useful.