I recently bought a 2011 Nismo. I started with the Capital One Buyer Network page:
Capital One Auto Buying - New Car Prices, Used Cars, Price Quotes
Within an hour I had four dealers offering to sell to me: 2 @ $500 below invoice, 1 @ $1000 below invoice and 1 @ $1500 below invoice. Ended up at $38,400.
Supply in CA seems limited now. Most dealers don't have any.
Even though this is a auto lender website, you don't need to get a loan (I didn't). The price was the same whether I used Capital One or didn't get a loan.
Alternatively, you may want to call 3 dealers, tell them the exact car you want and that you are ready to buy today. Tell them whoever offers you the lowest price by xx time gets the deal. I did that with the last car I bought and it worked quite well. Dealers were in a frenzy.
Take care to tell them precisely what price (car only, car + fees etc.) you want to see so everyone is offering on the same exact thing. I asked for a fax of the price page before I went in to the dealer so there wouldn't be any little "misunderstandings".