http://www.kayak.com/explore/ – – interesting map of the US and international destinations.
http://www.airfarewatchdog.com/ – – beginning to plan a trip to a city, two, or three (or more)? Start a ‘My Fare Alert’. I get weekly/monthly emails on the places I’d like to go to, just to see about their airline deals.
http://www.skyscanner.com/ – – new site I came across.
http://www.farecompare.com/ – – another compare fares site
http://www.studentuniverse.com/ – – if you are young and a student (college/university – or well, even high school now – it says 13+, but when I was younger, it was only for college students) check out this site. And purchase, also, a ISIC card – don’t miss out on discounts galore when you travel! I used it for when I went to Europe my first time. Speak with someone (faculty/staff) in the International Student Relations department at your school, that’s how I got mine.