Ask HN: what resources would you recommend to Project Managers?

I'm looking to brush up on my PM skills in preparation for a new job, and I've been gathering up some of the blogs, videos, books, and other media that has anything and everything to do with Project Management.

Then I thought: why not create a centralized resource that I could update for others trying to improve their own PM skills?

So here we are. Feel free to post anything and everything you have that you would recommend to a PM to improve their skills and give them new things to think about for their job.