From the homepage at macrumors :
Customers can begin pre-ordering all models of iPad mini and all models of the fourth generation iPad on Friday, October 26 through the Apple Online Store in the US, Australia, Austria, Belgium, Canada, Czech Republic, Denmark, Finland, France, Germany, Hong Kong, Ireland, Italy, Japan, Korea, Luxembourg, Netherlands, New Zealand, Norway, Poland, Portugal, Singapore, Spain, Sweden, Switzerland and the UK.