VoiceOver in languages other than English
The following description has been slighthly edited and put together, with permission, from several emails by Anne Robertson:
To get VoiceOver to work in a non-English language, you need to create a user in that language.
Assuming you already have VoiceOver working in English, you will need to create a second user, log in as that user, then change the language that user uses.
To create a second user, use the "Accounts" section in System Preferences - you'll need to unlock the padlock first.
When you have created your second user, log out of your main account and log in again as the second user. To select your language open System Preferences, go to the International pane and select the Language tab. Assuming you are using VoiceOver, interact with the Languages Table, go to the language you wish to use, use Drag and Drop to move it to the top of the list.
Drag and Drop: make sure that the VO cursor and the mouse are on the item you wish to move, press VO-Command-Shift-Space bar to pick up and hold the mouse, turn tracking off, move VO cursor to the place you wish to put the item, move mouse to VO cursor, turn tracking on again, press VO-Command-Shift-Space bar to release the mouse.
Select the third tab if you want to change the keyboard layout for this user also. Interact with the table and use Shift-click to select the keyboard layout(s) you want.
Check the Show Input Menu in Menu Bar checkbox. In this way, you can verify the existing keyboard layout and change it when you want to.
Note that when you change the keyboard layout from the Status Menu, it takes effect immediately.
Lastly, set the default voice for this second user to be one in the language you require and log out of that user.
You should now be able to log in as the second user and VoiceOver should function in the other language.
Anne reports success in using VoiceOver in French, but I haven't heard reports from anybody about how well VoiceOver is localised in other languages - does anybody have the knowledge to report about the quality of VoiceOver localisation in other languages? I can't find a document on the Apple website about what languages are supported.
Edited to add:
I received the following from Apple in response to enquiring about the localisations:
VoiceOver is localized in English, Spanish, French, German, Italian, Dutch, Japanese, and Chinese. Mac OS X ships only with English voices, but other language voices can be purchased separately.