I searched a lot to find a tutorial for drag & drop with jQuery alone (without UI), but due to the popularity of JQuery UI, all drag and drop features are based on JQuer
I understand this is an old post, but i was also interested in doing this without Jquery UI. I checked the links above, but i found this to be the best. It's only 8kb minified (UI sortable ~30, i've read), and is independent of any mammoth JQuery library (although those CAN make our lives easier sometimes).