Fairly obviously you could use wiki properties to sort you topics into categories, e.g.:

Category: FlexWiki tips

If, however, you were to use:

Category: "FlexWiki tips":http://<YOUR-MACHINE>/<FLEXWIKI-LOCATION>/search.aspx?namespace=<WHATEVER>&search=Category%3A+%22FlexWiki+tips%22

Then the property value will be rendered as a link to search for all the other topics in the namespace with that property value. Neat, eh?

I realise that dedicated topics which using the @@TopicIndex wiki behaviour would probably result in a rather more elegant solution, but unfortunately this seems to be broken in the current version (see here for details).

UPDATE: I've just corrected a minor type in the text above, but my first action in doing so was to double-click on the text of the post - maybe I've been using FlexWiki a little too much recently...