New answers tagged cropping
Look for Phatch (Linux, Mac, Windows), it's exactly what you are looking for : http://photobatch.stani.be/download/index.html
I can't believe no one suggested this yet: Just use the rectangular marquee to select what you want to crop down to, and COPY it to your clipboard. Then delete the entire layer and PASTE what you copied to a new layer. This is especially useful if the layer you're cropping is larger than the canvas, in which case the select-inverse technique is messy.
Top 50 recent answers are included