Check www.edmunds.com, latest incentives, manufacturer to dealer, for example:
2007 BMW Z4 - up to $7500.
2007 Corvette - up to $3000.
Plus, usually any car with big manufacturer to dealer incentives can easily be bought for dealer invoice minus any customer rebate and dealer incentive. They are trying to sell them.
For example, new 2007 Corvettes are selling for msrp/sticker minus $10,000 to $12,000.
As No1Piranah mentioned, the best deals are usually found at high volume dealers. They don't have to "hit a home run" on each car.