http://www.freestufftimes.com/wp-content/u.. -chips -locator -UPDATE-many locations are refusing to take this coupon now, so ymmv
http://www.mrtire.com/coupons/html/flat_repair.html -locator -thanks CavzGirl
http://www.nwa.com/worldperks/university/ -take the quizzes for all 4 courses to get them. Answers: Course 1 1) 500 2) 25,000 3) ALL Course 2 1) ALL 2) When following the link 3) Wait a few Course 3 1) True 2) ALL of the above 3) 14,000 Course 4 1)A NON-airline company 2)ALL 3)False
400 miles can get you free subscriptions to Allure, Coastal Living, Orange Coast, sunset, and This Old House . -there are a lot more if you wait for all 900 to show up.
You can also earn another 500 by linking with your delta skymiles account: http://www.nwa.com/worldperks/acctlink/#