theres always lots of grassroots motorsport around like motorkhana and khanacross, hillclimbs etc, but they are more fun than anything i think.
seems that most v8 drivers these days went through go-karting, open wheelers (such as formula fords), both of which seems to be relatively cheap forms, then perhaps touring cars in the UK or the development series of the V8 supercars (i forget the series name)
Main thing is skill, if you got that then you ll be head hunted no doubt.