Rally school:
http://www.gorally.com/
Cost depends on what kind of school you go to, how many days, and what type of program you are taking. It ranges from ~$700 - $3000. You might be able to find cheaper ones, but if you want to go for an scca license, make sure they are certified. All the above mentioned I've heard good things about. Panoz is another one to add to the list.
Nothing beats seat time, but if you're either serious about it or you can't afford a school at the moment, I'd suggest picking up a book or so on driving theory. That way, when you hit the track, you'll already know the theory and can concentrate on the application. I'd suggest the Skip Barber book or the Ross Bentley books. There's a lot out there though, so find what you can learn best with.