Screen Ruler is a full-featured, beautiful and useful screen ruler tool .
If you use the GNOME desktop, and are looking for similar software, then, Screen Ruler is the tool which you are looking.
Screen Ruler was wrote with Ruby language bindings of GTK + development, although small, yet powerful.
Not only have a variety of unit sizes, and can shrink and rotate, also supported the theme of customization. If you are a web designer, I think you need this tool.
Download the Screen Ruler:http://gnomecoder.wordpress.com/screenruler/