Once I realized we could have more than two “sidebar” blocks on the home page (because each of the two widget areas can have more than one widget in them), I moved the Map up to the first area with the welcome video (which, incidentally resolved a layout problem which was occurring in maximized Firefox, Chrome, and Safari, at least).
Then I wanted to put just something, for now, in the 2nd right area, so I put Categories there. (Which, as Bob noted, is sorted in a non-obvious manner right now.)
We should think about what might go there. Upcoming events is one idea I have, although we’d then want to exclude those from the main area of “Recent Updates”. There’s no easy way to exclude a Category, though, which I discovered when wanting to remove the Development Discussion.
Also, I’ve been wanting the Posts sidebars (on the Category pages) to be able to show only posts and comments from the specific Category, which also doesn’t seem to be a built-in capability. However, a couple of plugins listed on this page seem like they might give us more flexibility for those kinds of things. So I intend to try those.