This list doesn't intend to be a full listing of Drupal sites using the i18n module, but rather a collection of some sample sites.

• Canadian Treatment Action Council, English and French
• Christian Assemblies International, 8 languages!
• FivePaths, i18n + icanlocalize brochure site using English and Spanish
• Industrial Workers of the World, a union's site with 16 languages
• Khmer Software Initiative in English and Khmer
• QC Parawood company site in English, Japanese and Thai
• Reyero.net, the website of the i18n package author
• True BoxShot, software for virtual boxshots & covers creation. English & German localizations.
• WiFiHR, wireless network in Croatia
• AMNESTY, Amnesty International is a worldwide movement of people who campaign for internationally recognized human rights for all.
• Disorganized Trips, pictures and stories about traveling
• Socialist Party of Malaysia, website for a progressive political party in English and Malay
• Indian Classical Music
• The Sound Post, shop that repairs, buys and sells violins and other instruments

If you have some other good examples just post a comment here and I'll add it to the list.