Courtesy
foxgrrl,
ITA Trip Finder, the best flight search engine ever. It is not pretty. It provides no upselling tie-in deals with hotels, car rentals or cruises. It will not alert you to low fares to destinations you don't care about that you might have missed.
What it
does do, and that right awesomely, is provide hands-down
the best search interface for budget-conscious international travelers with some flexibility in their schedules (that would be me). Using their "month-long search" function, I can tell them "find me the best-priced flight of each day in a 30-day window for a trip approximately N days long." And it will do that. None of this "oh, we can only do this for the US and Canada" horseshit,
anywhere in the world. After about a minute, you get a simple HTML calendar view, with the best price in that period highlighted:

Then, click on any day in the calendar, and you get a list of all flights found for that day and trip duration, sorted by price or whatever else you want to search by:

"But wait, Meredith," I hear you say, "that's got to be a gimmick, they're not actually showing you the real prices with taxes and everything, are they?" To which I say
bullshit they're not:

Fare breakdown by leg, full breakdown of taxes, everything I could possibly want in a travel search engine -- including the exact booking codes so I can just call up the airline and say "oh hai, these two flights plz, kthxbai."
ITA, you're perfect. Don't ever change. I love you for your algorithms. Can we live the rest of our lives together like it's still Web 1.0?