While Imagecache is a stellar tool to automatically create and display resized and cropped images on your site, sometimes a bit more control is necessary.
Imagecache cropping is an automatic process that crops from the center of your image. So, if the most interesting part of your image is in the upper-left, it will most likely be cut off at least partially in the resulting image.
Imagecache Javascript Crop is a great little module that gives you manual control over exactly how the image is cropped. It provides a nifty widget that allows authors to precisely determine exactly how the image is cropped. Exposed as an ImageField widget, it's dead-simple to set up and a great tool in your arsenal of Drupal image handling.