What ONE writer's resource do I often consult? OMG, I have to choose?
Closes one eye. Clicks on the Bookmarks folder. Clicks on the Writing Resources folder. Clicks Open All In New Window.
Watches computer smoke, wheeze, and freeze.
Fiiiiiine. I'll limit myself to two. When I'm starting the book(s): Art Station / Deviant Art
I'm a visual writer. I write the movie playing in my head. I hoover up inspiration from these two artist-centric websites. Also the same places I look for cover artists when I'm shopping for illustrators. It doesn't matter the genre, the subgenre, or how far weird my rough storyline, there are thousands of pics that'll help crystalize characters and settings. Heck, some even shake loose plot twists. Beware the rabbit holes, though. It's easy to lose weeks to fantasizing about the next doorstopper.
Resists urge to link All. The. Resources.