For fun buy a new Mustang GT and install a blower. You can get about 525 HP. And the whole thing costs peanuts. Add some suspension and larger exhaust and a few other nick-nacks and it's fun time....
That's likely my next car, if I can get one. Supposedly Ford is being careful not to make so many that they become 'uncool' in too quickly.
In fact, they say the Shelby GT500 will be so scarce, you'll have to be friends with a dealer to even get one.
What I really want is a Bullitt in 2008, but I'm not sure I can hold out that long. Plus they haven't said what the price will be.... I can hack a Cobra, but if it's in the Corvette'$ range - that's too much!