To check Wine's translation status, visit this page - as of this writing, only 4 languages (Dutch, French, German, and Lithuanian) are fully translated.
Wine is different from most programs in Ubuntu - it doesn't use the standard Rosetta translation infrastructure. The reason is that Wine, internally, must use the same translation mechanisms as Windows. That means resource files, which in the Windows world require some manual adjustments other than simply changing strings.
However, if you don't like messing around with resource files, fear not! Several Wine developers have volunteered to do all the dirty work for you (even sending patches); all you need to do is translate the actual words. They send you a glorified text file (.po), and you send it back with your translations included.
It's very easy to get involved, just visit this page: http://wiki.winehq.org/Wine1.2Translations -- pick one of the developers listed there, shoot them an email, and tell them the language you'd like to translate for.