3. Real times in real time
Come the day of your trip, no site can help you avoid the hassles of getting from point A to point B as thoroughly as FlightStats.com.
The site has real-time arrival and departure information for almost every flight in the world, the latest security regulations, and up-to-the-minute weather conditions. It can send you text alerts if your flight is delayed, tell you which flights have the best on-time records, and even estimate how long you're likely to wait at the security checkpoint near your departure gate. Its mobile site is easily browsable.
And best of all, it's free.