pixel ruler

Can measure the distance (in pixels) between to points

Pixel-Zip decompressor is a raster image decompressor for the graphic arts

Ruler Bars is a pop-up set of vertical and horizontal rulers on your screen.

It's a screen ruler for Windows.

Calculate the sum of a selected number of pixels above a level threshold.

A Ruler for Windows is a free on-screen pixel ruler for your PC.

Cubic Ruler is a very simple to use screen ruler.

Free Ruler is a free screen ruler for Mac OS X.

Perfect Screen Ruler allows you to accurately measure anything on your screen.

On screen ruler, configurable for horizontal, vertical, centimetres, inches