For my illustrations I use:
Krita is really quite impressive as a piece of painting software. It lacks only a few of the features that I find necessary for a world-class painting application. I use it for anything painting or drawing related and is the core part of my workflow. I used to use GIMP. It is usable, but Krita is just a lot better for painting
I mostly use GIMP for Graphic Design stuff as I find Krita's text and selection tools clunky in comparison.
Just starting to integrate this. It’s a joy to use once you understand the workflow. Nick Saporito tutorials were really helpful for that. I am working on free and open source tabletop games, so most of my experience with it has been in designing icons for use in those.
I love Blender. It is the only open source graphics offering more impressive to me than Krita. I am not great with it, but I can model and sculpt enough to paint over and hide how mediocre I am at the above. I am trying to improve and would like to start to integrate Blender more into the composition of scenes and environments.
As for non-software, I use **[game-icons.net](http://game-icons.net)** a lot for random icons to use, as well as **[patreon](https://www.patreon.com/justinnichol)** to fund making open source art.