Grid System Generator is a website that asks for grid width, number of columns, margin-left/right & creates a fixed grid system with valid xhtml/css.
Besides the CSS framework, a .PNG background file is created as well to help in prototyping and design.



The generator is based on 960.gs & displays already created grids which can be found here.
You can also find instructions on using the generator & links to resources about grid systems.
P.S. Another 960.gs based grid generator can be found here.