Airside explains it’s process of creating their book Airside By Airside. The article features a section on the grid system used for the layout.
A lightweight grid system tool that generates a simple, clean and small CSS framework
The second part to Sigurdur Armannsson excellent article on creating grid systems in Adobe Illustrator. This article is based around the grid system developed by Marcus Gärde.
While grid design is a simple concept, there are now so many tools and ways of doing it that it might get confusing for newcomers.
Area 17 is a Brooklyn based studio with a gorgeous grid-based website.
An excellent grid tool that generates a PDF version of the grid.
A detailed article by Sigurdur Armannsson on how to create a grid system in Adobe Illustrator.
There is practically no (or very little) documentation about this problem on the web or in many typography or grid design books.
A free 4 Column Photoshop grid template for a 1024×768 screen resolution by Ray Gulick.