YouRule is a simple on screen ruler generator that I created. I original wrote a quick little Python script to make an onscreen ruler for the OLPC XO-1. It was so popular that I decided to put up a little web front-end to the script so that others could create their own rulers for own differently sized screens.
git clone git://projects.mako.cc/yourule
Please direct any feedack or commons to the author.
YouRule, like my other web applications, is distributed under the terms of the Affero General Public License.