The newest feature in Fine Uploader 3.1 includes the ability to upload folders via drag & drop. This feature is only available in Chrome versions 21 and newer. This is made possible by the File System API, which no other browser currently supports.
This API is still considered “experimental”, so it is conceivable that issues may arise in subsequent versions of Chrome, but I plan on following changes closely. As other browsers implement the File System API, support for dropping folders will be added for those user agents as well.
There is really nothing you need to do to allow your users to upload dropped folders. As long as they are running Chrome 21 or later, they can simply drop any folder they please. Some very large folders, or remote folders behind high-latency connections may take a few seconds to process. In this case a handy “processing” notice/graphic will appear until the files are ready to be submitted to the uploader.
Note that the uploader will process all files and directories under the dropped directory recursively.
I alo did some brief testing in Chrome Frame via IE7, but I am hesitant to claim support for Chrome Frame, so use at your own risk.
If you have any suggestions to improve this feature, please let me know by filing a feature or bug request.