I stumbled across a few tarot spreads designed specifically for writing projects and the need to use them as a NaNo prompt wouldn't let go! They're a bit more time consuming than the other prompts I've posted but may be less time consuming and more productive than banging your head against the desk as you struggle to figure out what should happen next ;-)
The spreads are all designed by Arwen.
The first is a Goal, Motivation, Conflict spread. She suggests it's best used during writing after you know your characters and when you're stuck on where they should go next. (Click on the image for Arwen's explanation of the layout.)
If your knowledge of tarot extends no further than the ability to place cards on a table, you can draw each of the 7 cards below and it will give you explanations.
Type in a Question like "Who is my character?" or "What is my character's goal?", under Deck choose a deck that sounds like it fits your story (you might need to explore them a bit), under Spread choose One card.
If you want to explore the possibilities for your main characters (or it might work for protagonist and antagonist), this spread can be used over and over. It's called a ladder spread because the top card (7) can become the bottom (2) card of the next set and so on up the ladder as you keep plotting your story out. (Click on the image for Arwen's explanation of the layout.)
Arwen also designed a Characterization Spread that delves into childhood and other influences on your character.
There are more Tarot Spreads for Writers at the Aeclectic Tarot Forum. Scroll 1/3 of the way down the page (or search for "writer".)
If using tarot for plotting intrigues you, there's also Tarot for Writers by Corinne Kenner that gets some great reviews.