1. Is there any documentation available on adding blocks / widgets?

I see that it has to be within an app.

2. Is it possible to create 'widgetized' area within a theme? I'd like add new sections other than the three existing on the forum home page.

Worked it out.

To answer my own question:

1. You can add widgets by creating a new app. I'm not sure if it's possible through just a plugin.

2. You can add the following code to your template:

{template="widgetContainer" group="global" app="core" params="'myCustomWidgetArea', 'horizontal'"}

I'm not sure if it's possible through just a plugin.

​Yes, plugins can also contain widgets.

​Yes, plugins can also contain widgets.

​Does the plugin widget appear within the widget list by default like in an app? I can't get it to show.