I've studied writing craft for over a decade. Here are some of my favorite resources for becoming a better writer (no particular order):
1. Creating Character Arcs by KM Weiland combines character and plot to create a workable story structure (see her entry under websites below for more)
3, Bird by Bird by Anne Lamott. I go back and forth with this one. Sometimes I think it's an excellent, relatable resource, and sometimes I think that the author sounds neurotic. Either way she has some great tips and motivation to keep writing. Some content is for adults only.
4. Writing Magic by Gail Carson Levine is written specifically for younger writers, but there is plenty for seasoned ones too!
5. Writing the Christian Romance by Gail Gaymer Martin. I checked out this book from the library about three times before getting my own copy. I don't write Christian romance, but I do keep my romances clean and wholesome, and this book is a great resource for that.
6. The Writer's Digest Handbook of Novel Writing. This is an older collection that's out of print and tough to find, but it's a collection of useful articles. I frequently quote Orson Scott Card's section on how to transition from writing short stories to full novels.
7. The Emotion Thesaurus by Angela Ackerman and Becca Puglisi is a great resource that teaches you to use physical cues to show emotion instead of tell it.
9. The Elements of Style by Strunk and White is a classic for writing advice, specifically "making every word tell".
10. Writing Tools by Roy Peter Clark is both entertaining and informative, an excellent resource for writing craft.
11. Word Painting by Rebecca McClanahan instructs on writing descriptions, and the writing of the book itself is an excellent example.
13. The Seven Basic Plots by Christopher Booker is a huge guide to genre and the evolution of stories. It discusses Jungian archetypes as well. Beware: this is an extremely long read.
16. Gail Carson Levine has a blog where she posts biweekly writing advice. Writers can ask questions in the comments section, and Gail and others will give excellent advice. Gail will mark some writing questions as subject material for future blog posts. It's a supportive, helpful community.
17. KM Weiland has a lot of writing articles on her blog, especially about story structure. Some of the articles have turned into books (see my books section above), but all of the information is free on her blog.
19. Brandon Sanderson puts his entire university course on writing on youtube for anyone to watch. It has a focus on sci-fi and fantasy, but includes all kinds of helpful advice.
20. Hello Future Me is a great resource for writing tips and especially for worldbuilding.