MOBZRuler is the .NET successor to gRuler (previously known as DXRuler), now hosted on CodePlex. It overlays a grid and the most common display sizes on screen:

MOBZRuler on top of the Google Home Page

There is just one menu that says it all:

The MOBZRuler Menu

Download MOBZRuler

Download MOBZRuler Download MOBZRuler 1.0.3 (April 26, 2011) from CodePlex or browse source code

Windows Installer, 350 kB, requires the .NET Framework 2.0

Comments? Bugs? Suggestions? Feature requests? Let us know! Alternatively, you can create a work item on Codeplex.