There's a new Locale Builder for creating your own custom locales live on the Download Center at http://www.microsoft.com/en-us/download/details.aspx?id=41158. The direct link to the setup exe is http://download.microsoft.com/download/C/6/8/C68BDDC5-50CB-47E1-9EF7-B5651D68BDDF/LocaleBuilderSetup.exe
Locale Builder 2.0 is designed primarily for Windows 8.1/Server 2012 R2, including a few new data fields for those locales. The constructed locales might work OK on previous versions, or they could have slightly strange behavior.
"Locales" are what Windows uses to provide date formats, time formats and the like for users and applications. So things like clocks and number formats in Excel. These are values you might need to write a letter or run a report and have the right format for the date. Locales are a subset of the common data that applications use for day to day formatting. Other strings you might see on the computer are done by either the application or operating system localization, which beyond what the Locale Builder was designed for.
What can you do with the Locale Builder?
Hope you find the new Locale Builder 2.0 useful!