Google has had drag-and-drop to upload files to Google Drive, upload pictures to Google docs and sites, and other drag-and-drop capabilities, for a while now. This makes it easier to use and work with these apps. Google just recently announced that you can now also drag-and-drop to upload folders to Google Drive. This makes Drive a much more usable cloud storage option and makes it easier to add your files to your Drive.
For more information: http://support.google.com/drive/bin/answer.py?hl=en&answer=2424368