Do you speak a language that is outside of the usual "top 40" languages spoken internationally? More importantly, do you know the locale-specific issues like how date ranges are written (May 3-5, 2008)?
You may have heard of Unicode, the replacement for ASCII that lets you type in hundreds of languages. Did you know that the same organization maintains the Common Locale Data Repository, which includes machine-readable definitions of how dates are represented, words are sorted, and so on. The latest update is going to attempt to include even more attributes: not just the date format, but the format for date ranges; not just how to alphabetize words, but the alternate sorting rules used in that country's phone book, ...
The Unicode CLDR Project has set up a web site where people can review their current data and submit updates.
I think it is great that they are opening the project and searching for volunteers. A project like this can only be done with the power of the open web.
The project's homepage: http://unicode.org/cldr/
Anyone can view the data. You only need to create an account to report updates or make suggestions.
If you are interested in what kind of bugs are being reported, view the recent submissions here.
If you know a particular language or culture very well, please volunteer!