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 imgur.com,
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/