This works reasonably well only on computers with a lot of memory as all images are loaded into page in full resolution, but even there it will be sluggish so be patient. It will not work well on smartphones or tablets. Select crop using mouse (the first corner of rectangle is defined by clicking and holding mouse button pressed, the second is defined by releasing button) or click on links for common crop locations:
Smaller:
Center crop
Top left DX corner crop
Bottom right DX corner crop
Top left FX corner crop
Bottom right FX corner crop
Larger:
Center crop
Top left DX corner crop
Bottom right DX corner crop
Top left FX corner crop
Bottom right FX corner crop
Nikon 24-120vr
Tamron 70-300vc
f/04.0
f/04.5
f/05.6
f/08.0
f/11.0