Had a very interesting visitor yesterday: Jago Dodson from the Urban Research Program at Griffith University in Australia. Jago has published research on measurement of Oil Vulnerability in Australian cities eg:
Oil Vulnerability in the Australian City: Assessing Socioeconomic Risks from Higher Urban Fuel Prices (Dodson and Sipe, 2007)
Shocking the Suburbs: Urban Location, Housing Debt and Oil Vulnerability in the Australian City (Dodson and Sipe, 2006)
Oil vulnerability is measured by combining various census variables (mode of transport to work, number of cars in a household) and socioeconomic data (SEIFA) to produce the VIPER (Vulnerability Index for Petrol Expense Rise).
The VAMPIRE (Vulnerability Assessment for Mortgage,Petrol and Inflation Risks and Expenditure) is a measure of oil and mortgage vulnerability and includes mortgage information.
I decided to try this for a NZ city. Here is a quick lo-res attempt at an Auckland VIPER:
VIPER index from 2006 census data. Dark = more vulnerable to oil price increases. Light = less vulnerable.
Now I just need to find some mortgage data, cause even though VIPER is a pretty cool name, I love the idea of creating a VAMPIRE index!
who where why 
Neat, which data sources did you use?
I used 2006 NZ census data (proportion households with >=2 cars, mode of transport in trip to work) and NZDep 2006 (from PHI MOH). Will put the source data and VIPER index up on http://www.koordinates.com a bit later.