If the Photoshop file containing multiple grid systems I shared previously is not enough for you, here is a plugin for Photoshop that enables you to create and customize any sort of grid system for your layouts.

Free Download

This file contains 21 grid systems for your webdesigns, all 960 pixels wide with different columns number, gutter width and columns width.

Free Download

If you want to go wild with 960 pixels wide grids, check this online grid calculator