One important clarification guys. Upon re-reading Mark's post, I realize there are two parts to this:

1) TOPICS FOR OBJECTS: The screen shot Mark posted shows the Community Management Console being used to add

to individual knowledge articles. These are stored in the TopicAssignment object, which IS available from SObject. A few key things to remember:

- These are Community-scoped. If you use Workbench to query TopicAssignment, you will see the NetworkId field. The topics you assign to articles in the Community Management Console will contain the ID of the Network (community) you are in at the time. This is important.

- The EntityId field contains the Salesforce ID of the article (e.g. FAQ_kav) you are tagging. When used with other objects, that field contains the ID of the records or FeedItem the topic was tagged to.

- TopicId contains the Salesforce ID of the topic you are tagging to that record.

Tagging a knowledge article with a topic (in the current community) makes it appear on the Topic Detail page under the Articles tab/component.

2) MANAGED TOPICS: As described above, you can set individual topics to be in the navigation and/or featured. This is the process I described above, and is manageable through the REST API of Chatter Connect.