What's the best way to buy a car over the Internet if you can't go see it?

I'm not talking about Ebay here. I'm in negotiations with a Private Party through email to purchase their used car. I've seen pictures and done research checks, and things seem on the level. However, with all the fraud and scams going on, I need to know the safest way to actually send the money, other than in person, and be sure of receiving the car? Any suggestions?