Here is the official list from http://www.xbox.com/en-US/live/countries.htm 

• Australia: International English
• Austria: German
• Belgium: Dutch, French
• Canada: English, French
• Denmark: Danish
• Finland: Finnish, Swedish
• France: French
• Germany: German
• Hong Kong: Traditional Chinese, English
• India: English
• Ireland: International English
• Italy: Italian
• Japan: Japanese
• Korea: Korean
• Mexico: Spanish
• Netherlands: Dutch
• New Zealand: International English
• Norway: Norwegian
• Portugal: Portuguese
• Singapore: International English
• Spain: Spanish
• Sweden: Swedish
• Switzerland: German, French, Italian
• Taiwan: Traditional Chinese
• United Kingdom: International English
• United States: English

Greece has a petition out.  What countries/languages should MSFT support for the future expansion of Live?

Rumenia, I heard there were also a petition.

U mean Romania?

Wait, there are some countries with Xboxes that can't get on Live?

Then my answer is, obviously, all of them.

Possible don't know all the English names of the countries on this world =p.

Guam, since it's a part of the US, and M$ doesn't seem to know this.