I've been playing around with some of the new HTML 5 FileReader and drag & drop code available in modern browsers and I've put together a 'proof of concept' block for Moodle 2.0.
With this block installed, you can drag files from your desktop onto a section of a Moodle course, where they are converted into resources (using the file name, minus extension, as the name of the resource and defaults for everything else).
If anyone wants to have a play, then the code is here: https://github.com/davosmith/moodle-block_dndupload
It needs Moodle 2.0+, a course with the 'topics' format and a recent version of Firefox or Chrome (I've not tried Safari/Opera, and I know IE won't work).
It is also likely to be full of security flaws in the way it uploads the files and everything else, but it should install cleanly and it does work (on my dev box). Full instructions are in the README file (along with several repeat warnings that this is not intended for production use - consider yourself warned!).