Grid Resource #1 MDN
MDN is my goto site for learning. I haven't found a web development topic that they don't cover, and of course grid display isn't an exception.
Grid Resource #2 Grid Garden
I found this one last week when looking at Flexbox Froggy. I signed up and started playing it and had to quit before I got through. Like flexbox froggy you have to enter the code to accomplish a movement on the corresponding screen. There are 28 levels to this game, and they increase in difficulty with each level.
Grid Resource #3 Quackit
Just like with last weeks flexbox assignment I'm placing quackit.com between the level of Grid Garden and MDN for the level of information available. While MDN is a wealth of information, sometimes it's nice to just get the 10,000 foot fly-over instead. quackit.com does a good job with that. There are code examples that you can play with, and a decent enough tutorial that starts with the history of grids, and ends with browser suport documentation.
Grid Resource #4 Griddy
Because I reused the three resource from last week for this assignment I thought I would include a 4th to make up for it. Griddy is a free tool that allows you to create grid layouts with a GUI interface so you can see your grid in real-time as you change attributes. Under the GUI grid layout the code is supplied so you could just copy and paste. Griddy supplies drop down lists that allow you to change everything possible with grid layouts from number of columns and rows to alignment options. While it's pretty basic, it was kind of neat to see the grid form in front of my eyes.
Summary
I did a google search for "css grid layout tools" and google returned 29,800,000 results! Obviously I didn't look at them all to see if they were pertinent or not, but that number certainly says a lot about how much information is available on the subject. I'm sure I could spend the rest of my semester doing nothing but reading articles and playing with tools for grid layout and not even scratch the surface.