Primarily... I just do figure studies outside of specific projects. Line of Action's practice tools is great for that. Has a variety of body types and poses and specific options like only-hands/feet/expressions or clothed or unclothed, and you can set it to run like a typical figure drawing class with 30 sec warmups leading into the last long study, or you can just have endless short timed poses or something. Since I don't have access to live models at the moment, this has been a great tool for me to try to keep up practice.

When I need specific pose references for something I just cannot figure out, I'll either google for what I'm looking for which often lands me in places like SenshiStock, or try to take a ref myself if I can't find it, but I don't really have specific go-tos online.

Book-wise:

Atlas of Human Anatomy for the Artist, Vilppu's Drawing Manual (kind of seems like an art school staple, I hear it recced a lot and used it in class myself, though I either don't own it anymore or have misplaced it somewhere hah), Master Class in Figure Drawing, Anatomy: A Complete Guide for Artists - These are all my favorites for breaking down the human figure and learning to draw it either via simple shapes or getting into detail on muscles and how they work and how to draw them.

Facial Expressions: A Visual Reference for Artists - Nice in that they take a model and shoot them in a ton of different facial expressions, so you get the same sort of facial expressions for a variety of features.

Atlas of Foreshortening - This is an excellent reference book for weird foreshortened poses that I've found difficult to find online.

The Artist's Guide to Drawing the Clothed Figure - Great for learning to draw fabric, especially the way it hangs on people, but also just in general.