drag to move
drag handle to move
drag to move
vertical constraint
drag to move
horizontal constraint
drag to move
contrained to region
drag to move
exaggerated drag threshold
drag to move
absolutely positioned, constrained vertically and within visible area
Update 4/26: tested and working as expected in IE6, Firefox 1.0, and Safari 1.3, unless otherwise noted.
Safari 1.2 leaves visual artifacts on the background while dragging.