Visual Novel Resources

Kopacurve UI - Free visual novel GUI (full sets & UI elements!)
Dova Syndrome - Free BGM & SFX (use the advanced search, it's really good)
Hurasuko7317 Booth - Motion graphics & sprites
mjshi - RPGMaker plugins, PLUS skill icons, music, re-usable code, etc all by one individual!!
Feniks - Ren'py developer of amazing tools like music players & achievement handlers. They also have a website with tutorials and other resources!
Acon3D - Website for free & paid 3d models, usually in Sketchup. Great for backgrounds!

Website resources

remi.resources - Tumblr blog with a bunch of cool banners (big focus on assets for writers!)
doqmeat.com - website with a TON of resources like reusable code, pixel art, banners, & more!