Cross-browser drag-and-drop HTTP file upload?

I'm looking for a cross-browser html file uploader with drag-and-drop capability. Ideally the drop target area can be large and overlap other elements (ie. I'd like to allow the user to drop the item on existing parts of the HTML UI instead of requiring a separate target area).

Cross browser support (including IE6) is important, as is reliability. I'm using jQuery, but am open to good solutions that don't use jQuery.

Any recommendations?