What's that animation mod I see people using where they pose their characters for screenshots and stuff?

Hope this is the right place to ask...

I think you're looking for Director's Tools, which will also need some extra animation behavior files listed with it.

There's also Pinup Poser.

And also Puppeteer Master which has spells for NPC's to do animations.

FNIS is also one, though it has idle animations instead of poses.

cheers )