Since I’ve been trudging away at making something using Twine over the last few months, I checked and couldn’t find a good list of resources for Sugarcube on the forum. Harlowe has this useful thread, but there doesn’t seem to be anything showing up immediately for Sugarcube. Instead there are a lot of threads asking for help on Sugarcube, so I figure a good thread of actual resources may intercept at least a few of those postings.
Starting with the absolute basics: the Twine Cookbook is general documentation for Twine as a whole, including many commonly-needed tasks in a variety of Twine formats (including Sugarcube). It contains guides for things like incorporating Google Fonts, but doesn’t do a good job of explaining how the Sugarcube format itself functions. That’s covered better by the Sugarcube Documentation on the creator’s website, which does an excellent job of breaking down the basics of how to do things in the format.
That’s not all that’s out there, however. A lot of people have made plugins that you can, well, plug into your Sugarcube game to make it so you can use various functions without having to code them from scratch yourself. The one I’ve made the most use of is Chapel’s Custom Macro Collection, and it appears that they’ve also developed a plug-and-play Inventory System as well. Their site also has a library of resources for additional macros and modules.
For those needing a very basic, tutorial-style textbook approach, GrimBaccaris’s Twine Grimoires are free step-by-step walkthroughs of the basics of Twine. Both Sugarcube and Harlowe are covered in a general sense, though not in any sort of depth. Very good for those needing to start from the very beginning however.
As a useful thing to know which is not expressly covered in the above, you can incorporate SVG vector images directly into Sugarcube - either directly with pages or called via a widget. A good library of free SVG icons is at Game-icons.net, and any of them can be freely used via basic Creative Commons attribution. If you download the SVG from that site and open it in something like Notepad, it will give you the full HTML SVG code to render that SVG - all you have to do is copy/paste the code into the relevant space to get exactly that vector image.
Anyone else who has anything they wish to contribute, feel free. I hope this helps some people who may be struggling with the same things I’ve already managed to find solutions for.