I wanted to share an extension I made to generate guides in a grid - resulting in equal width columns with gutters (= spacing between columns). I named it Grid Maker, and you can find a more detailed description and a download link on the Grid Maker github page. Here is a direct download link. (Is there a particular place to announce extensions other than this forum?)
The extension in action:

My extension is heavily based on the extension Grid Creator, which generates guides in relation to the page/document. I used that extension as a base to suit my needs - grids (for designing websites) that can have gutters, and that can be centered in a page (or left or right aligned). It also works with rows.
It is my first extension and I'm not a programmer, just a designer tinkering with code.
What do you think ?