Hello,
I had needed in previous project for a crop tool with a specific features witch I think you are interested on it too:
1) The crop area or the image is movable, most of plugins allow only the crop area to be movable.
2) The crop area can resized, this is very important, during my search i found the area has a fixed size, but this two plugins are the best in market plus they are free.
jQuery Cropper.
imgareaselect.
If you are interested, can provide you examples, also I would like to see your site, so I can determine the best way to integrate this crop tool.