seobook.com has that overture tool and has been modified to display results for google, yahoo, msn, etc.. and that site has many free tools and valuable information
Bid on "specific" brands vs. generic words "sports cars" or "european cars". If I were you I'd check out say the Lexus or Benz or whatever websites or a dealership and get a list of inventory names.
So let's say there's the Lexus XYZLx2456 brand or the Mercedez J45s4Mx 2007 (lol I am a chick so I don't know cars, lol) - bid on that for some cheap targetted traffic. Also try car dealersips like "Joyce's Mercedez Dealership, New York City" or whatever. Someone wouldn't type that in if they weren't in the market for a car. And if they are thinking of buying an expensive car, chances are they are interested in your reviews, what others have to say, etc.
Also think about next year's. Aren't next year's (2008) brands coming out? So maybe you can contact the dealers and be the first to review the Porshe HKX219 brand or whatever. So if someone types in "Porshe HKX219 2008" not alot of people will have sites about that and they will come to you.
Just some ideas. Also, if you are going for Adsense revenue, you may start off with the generic names like "Porshe, Lexus Mercedez, etc" and see what the EPC is like (i.e. make sure to have some good content around the ones who are paying well).
Also, you can check out Keywordspypro (NOT Keywordspy plan because it is a good $30 more expensive) and get the keywords of top car sites and keyword country. There's a free 6 day pass to Wordze that one member here was talking about (use the "search" function).
Also think about bidding on domain names like lexus.com or porshe.com or "luxurycars.com" or whatever (people type these names into the search box). Also think about mispellings.
The average person is too lazy to do any of the "out of the box" thinking so if you do, it should pay off well.
This is advice culled from a superaffiliate (and tried with some success by myself) -
Keyword Research Secrets to Explode Your Affiliate Business | Super Affiliate Mindset
Good site by the way.
Best of luck!