Every browser game out there is available on several languages. But translations cost a lot of money and may not be available on small budget projects. On our project we have mechanisms for presenting the user interface in several languages. We register the tokens per language on a XML file and when rendering we use the current language tokens.
We translated the game ourselves to English and Portuguese. Then we decided that we should try to use our players to help us with more translations. we set up the Orion's Belt Translation Project, were any player can register and contribute in translating tokens to his language.
Translating may be a hard a boring work, so we compensate the players by offering Orions (the game currency). This way everyone gains from this interaction.
The system is paying off and our space browser game is now available on Croatian, and it's being translated to French, Italian, and several other languages.
The only problems with this solution is that it will take longer to get translations ready and we really don't know if they'll have substantial quality.