Check out the new Editor's Guide wiki in the documentation section. Built by the community for the community - how cool.
Back in an earlier blog post this summer we asked for people to volunteer for several initiatives we had going on. Mnkras spoke up as willing to lead the Editor's Guide project and with his team we now have a page for each and every part of the editing UI. Once we get 5.5 into Alpha/Beta we will have to update all these pages and also launch a dashboard section. We'd love more help so if you have some time and interest let us know.