At DrupalDownunder some years back, the wonderful Erica Bramham named her talk "All node, no code". Nodes were the fundamental building blocks in Drupal, they were like single drops of content. These days though, it's all about entities.
I gave a talk a couple of years ago called Tools for Talking.
I'm preparing a new talk, which, in some ways, is a sequel to this one. As part of that prep, I thought it might be useful to write some short summaries of each of the tools outlined here, with links to resources on them.