Hi, I'm a NZ Citizen, living permanently in Australia. I arrived in the US in May 2001 intending on only staying my 90 days allowed, I over stayed. I married a US citizen, but we have since divorced. I returned to Aus in Sept 2004.
I would like to return to the US to visit family and friends but am unsure if I need to apply for a visa or if I can just go as I still travel on a NZ passport?

Any light on this would be greatly appreciated

Cheers! :)

If you are coming for 90 days or less you should qualify for the visa waiver program, since both NZ and Australia are included in the program. You will need to obtain authorization through the Electronic System for Travel Authorization (ESTA). See: Visa Waiver Program (VWP) According to that web site, you may be denied if you have previously violted the terms of the Visa Waiver Program. Given the violation of your visa back in 2001 you may find that you are denied.