Depends on where you are going, really. Within Europe, try RyanAir or EasyJet. Fly to London from US is not that expensive, then continue on with these flights.
For Asian travel, I prefer to call 1-800-2-BORNEO (This is an Indonesian travel agent, but they speak English, of course ).
I recently purchased a ticket from Atlanta-Jakarta (during Christmas and New Year) for $970, saving about 600 bucks.
Asian tickets
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