Both Draftsman and GuideMaster from AV Bros. look to be very useful for users of Photoshop when the need to create horizontal and/or vertical grids arises, which is damn near every project. Draftsman creates selections within your document, while GuideMaster places guides. I just downloaded the demo versions of each to tinker with them and have been pleasantly surprised. There are a couple of features I would like to see, namely I think Draftsman should provide the option to output as vector objects instead of selections. Also, I think it should mimic Guidemaster’s functionality which allows the designer to use percentage-based values (one third, a quarter…) in addition to the currently supported fixed values (24px). I need to do a bit more testing, but one, if not both should prove to be a worthwhile investment.