Ask HN: What are the resources you most frequently recommend?

For example - the manager tools podcast is excellent. I see that it's recommended 3+ times in this thread https://news.ycombinator.com/item?id=18264245. I'd sent it to friends quite a few times, but there hadn't been a good way for me to share it with the wider community online. Product Hunt didn't seem suitable because it's not my product, and submitting a link to a podcast never seemed like something appropriate to HN. So perhaps this is a good use for a thread. What are the resources you most frequently recommend?