Rectangular Marquee Tool
http://marqueetool.net/

Marquee tool is a Javascript application that can save you time and help you in your future projects. It is the first web based Javascript tool that allows you to select rectangular areas on div or img src=”” / elements, calculate selection coordinates, display them or send them to the server. The next version of the Marquee tool, “planned for release by the end of the March” will give you the ability of managing several Marquees on the same picture. Marquee tool uses a reduced size version of Prototype Javascript library, producing a smaller size, extremely functional and fast loading in browser. The total size of the application is about 50KB. Tool is the free for use and distribution application and it doesn’t require developer permission or approval to use. This has been added to World Wide Web Reference Subject Tracer™ Information Blog.