An alternative to Yoink and DragonDrop. Yoink is still a better choice IMO; however Dropshelf has few cool features that are not available in Yoink such as multiple shelves; dragging to any edges.
Yoink has a great feature which I don’t know why none of the like-apps haven’t considered adding: “move window to mouse location where drag is initiated”. It helps a lot in reducing mouse cursor movement.
The last alternative, DragonDrop, on the other hand, is very buggy and use a rather ‘inconvinient’ method (shake the mouse cursor) for displaying the drop window. The last update of DragonDrop was almost a year ago (06 August 2012). I would not recommend you to buy this. Use Yoink or Dropshelf instead.