Yesterday after discovering it on Xavier Roy’s site I was reminded that the Post Kinds Plugin is built on a custom taxonomy and, as a result, has the ability to output its taxonomy in typical WordPress Tag Cloud widget. I had previously been maintaining/displaying a separate category structure for Kinds, which I always thought was a bit much in my category area. While it’s personally nice to have the metadata, I didn’t like how it made the categories so overwhelming and somehow disjointed.
For others who haven’t realized the functionality is hiding in the Post Kinds Plugin, here are some quick instructions for enabling the tag cloud widget:

In the administrative UI, go to Appearance » Widgets in the menu structure.
Drag the “Tag Cloud” widget to one of your available sidebars, footers, headers or available widget areas.
Give the widget a title. I chose “Post Kinds”.
Under the “Taxonomy” heading choose Kinds.
If you want to show tag counts for your kinds, then select the checkbox.
If necessary, select visibility if you want to create conditions for which pages, posts, etc. where the widget will appear.
Finally click save.

You’ll end up with something in your widget area that looks something like this (depending on which Kinds you have enabled and which options you chose):
The tag cloud for the Post Kinds plugin data
If you’re interested in changing or modifying the output or display of your tag cloud, you can do so with the documentation for the Function Reference wp tag cloud in the WordPress Codex.