MacRumors.com

Think Secret says the the iTunes Music Store should have an October 26th rollout into several European countries, as well as Australia and other venues. Various MacRumors readers report that the iTMS is currently unavailable for browsing from their countries today, suggesting the localizations for them may be just around the corner. Those reports include Switzerland, Austria, Ireland, and Canada, with users being greeted with a new message stating "iTMS is not available in your country yet."

[Update] - Additional countries as reported by MacRumors.com readers
Spain
Norway
Finland
Netherlands
Sweden
Japan
Italy
Belgium
Poland
New Zealand
Denmark
Mexico
Iceland

[Update #2]The official list as of 9 a.m. PDT includes Austria, Belgium, Finland, Greece, Italy, Luxembourg, Netherlands, Portugal, and Spain