Jcrop - Quick and easy image cropping with jQuery.

Jcrop from Deep Liquid is a quick and easy way to add image cropping functionality to your web application.

Jcrop from Deep Liquid is a quick and easy way to add image cropping functionality to your web application. It combines the ease-of-use of a typical jQuery plugin with a powerful cross-platform DHTML cropping engine that is faithful to familiar desktop graphics applications.

• Attaches unobtrusively to any image
• Supports aspect ratio locking
• Supports minSize/maxSize setting
• Callbacks for selection done, or while moving
• Keyboard support for nudging selection
• API features to create interactivity, including animation
• Support for CSS styling

It's definitely one of the best one's I've come across. It's about 5.5KB (minified), compatible with all browsers and its free (MIT license)! Check out the demos.