[AndrewHampton]

I'll drop in the customary link to hammerspoon: http://www.hammerspoon.org

It has a couple libraries for window management. One is plug and play, the other is lower level. Here is my config for setting up a 2x2 grid: https://github.com/andrewhampton/dotfiles/blob/master/hammer...

[tnajdek]

Another one is called slate: https://github.com/jigish/slate

Very flexible, my favorite feature is that configs can be written in JS, here's mine: https://gist.github.com/tnajdek/48ea2a2ccac365b91f29

[zdw]

Slate is my favorite as well - there's a fork that accumulated a bunch of patches over the years as the original author appears to have abandoned it:

https://github.com/mattr-/slate

Unfortunately, it was declared unmaintained as of a few days ago...

[lowboy]

Yup been using Slate for a while now. I wrote a grid system for it that I find works well: https://github.com/jjt/ac-slater