If you’re flying anywhere in the next few months (say, Thanksgiving or oh, Christmas) and Northwest Airlines is an option, check out the 50$ rebate that Paypal is offering on bookings. You have to book between November 13th and 21st, but the terms and conditions don’t stipulate when you have to fly.
As with most other rebates, you’ll have to wait 6-8 weeks for your money to show up, but the benefit here is that you don’t have to fill in any paperwork or cash a check — the money just shows up in your account in a few weeks. And if you’re like myself and most of the other people out there on the interwebs, you’ve already got a Paypal account that’s linked to your bank; all you have to do is select the Paypal option, the money comes from the same place and you get 50$ back.
Make sure you follow the booking link before you pay.