CNNMoney has an article on the best time to get things like airline tickets, TVs, and more. I'll cut to the chase here - read the article for more detail.

Best times to get stuff:

Airline tickets: Wednesdays. Try to get 2 weeks before, or otherwise within just a few days of the trip.
Why: List of available seats released Wednesdays; Tickets expensive 7 to 14 days before a trip.

TVs: Spring, beginning in April.
Why: Japanese market cycle releases new models in April - old models get discounted.

Houses: Winter
Why: Less demand, better deals.

Cars: End of the month; Winter.
Why: Dealer quotas; Less demand, better deals.

Video Games: 1 to 3 months after the holidays.
Why: Holiday hype died down - discounts.

Toys: After the holidays; August.
Why: Discounts; Clearing large inventory to make room for holiday rush.