Human Poses & anAtomy

AdorkaStock - Pose reference library

PoseMy.Art - Virtual pose mannequin

Quickposes - Pose library and gesture drawing app

Animal Poses & AnatoMy

Horses Inside Out - Horse training and anatomy site, lots of quality pictures for learning equine anatomy.

Fontspace - Fonts, filterable by usage, style, etc.

The Public Domain Review - Public domain images, books, audio, and video

Unsplash - Royalty free stock photography

GIMP - Open source photomanipulation software

Nightshade - AI data poisoning tool

Photopea - Free, online photoshop clone