The most underrated resource for concepting
There are tons of Art Director resource collections out there. They round up the usual suspects, but rarely do I ever see this amazing resource mentioned: The Deck of Brilliance
It's a simple collection of "Idea Generation Tools for Creative Professionals," by Juggi Ramakrishnan and Todd McCracken.
Here’s how they describe it:
The Deck of Brilliance can help you face that blank page and looming deadline with a bit more confidence. It gives you 52 tools for working up ideas in short periods of time… Without a systematic way of approaching briefs, you risk leaving the outcome to chance, a random spark or a burst of inspiration in the shower. Professionals don’t leave things to chance. They don’t wait for ideas to come to them; they hunt them down where they live. These tools are the result of over 50 years of experience in the world’s toughest advertising markets. We’ve refined them over many years and we use them ourselves, almost every day, to hunt.
Clicking on a card will bring up tons of examples of the trope:

How amazing is that? I hope this thing stays online forever. Every creative should know about it and be grateful for it. This is one of the things I look at and think, “Man, I wish I made that!”