In my years of doing work, I've accumulated a number of assets and resources that have helped me and that I know will help others. As a note, assets available are either Free Use or CC0 so they can be used in your own personal works legally. All links provided are services or tools I have personally used and have experience with.


Subtle Patterns: A nice collection of textures suitable for backgrounds for almost anything
Pattern Cooler: Generate all types of patterns using your own color choices


Tyodermic Fonts: All fonts offered, free or paid, are permitted for commercial use.
Blambot: Resource of comic focused fonts and lettering how-to


Line of Action: Great resource for all kinds of gesture sketching exercises.
Elftown References: Old site with a large collection of reference images of all sorts of things
Senshi Stock: A robust collection of photo stock images for use or referece


Jetpens: The best place to purchase any sort of drawing or writing tool
Medibang Paint: free digital art program, for all platforms, including mobile
Krita: Free digital art program for all computers
Graphics Gale: Free pixel art program for Windows
Aseprite: 15$ pixel art program for all computers