This application allows you to capture the entire screen, the active 
window or a selected region. You can set the delay that elapses 
before the screenshot is taken and the action that will be done with 
the screenshot: save it to a PNG file, copy it to the clipboard, open 
it using another application, or host it on ZimageZ, a free online 
image hosting service.

A plugin for the Xfce panel is also available.

You can grab the development version on git.xfce.org by running:
git clone http://git.xfce.org/git/apps/xfce4-screenshooter/

The documentation is available in the doc/ folder of the source tree.