Buy plane tickets 3 weeks in advance

I find this interesting. From NPR's Business Story of the Day:

"IF you are planning a trip you will probably get the best airfare if you book your trip in the middle of the week about three weeks before your departure. You want to look at Wednesdays specifically because thats when airlines tend to start running their fare sales, and you want to look about twenty-one days out because airlines know that people tend to plan either far in advance or very much at the last minue so twenty-one days out is when you're going to see the lowest prices."

Also the best time to buy a new car is September.
The best time to buy gas when prices are rising is before 10am.
The best time to buy gas when prices are falling is after noon.