For anyone whos gone to the msdn library (http://msdn.microsoft.com/en-us/library/ms460356.aspx) to find out what the IncludeFolders attribute on <Module> is for and been confronted with the description
“Optional Text.” (not helpful)
Here’s what I’ve managed to uncover. If you have a file (a.txt) and you’ve popped it in a folder (en-gb) in your feature folder you can reference it like this:
<Module Name=”TestFileDeploy” Url=”Style Library” IncludeFolders=”en-gb”>
<File Url=”a.txt” Name=”a.txt” Type=”GhostableInLibrary” />
</Module>
Now some of you may have spotted where this is going as “en-gb” and “??-??” have a similar format. 
If you multiple language formats for the file, and hence have multiple language folders in your feature, all you need to do to deploy all your files is change the IncludeFolders to “??-??” and it will bring them across. You don’t need to add loads of <File> tags as its covered by IncludeFolders=”??-??”. Fantastic!
