I have lots and lots of content on my site, and I'd like to be able to showcase some of that content better. One way to very easily to that would be to put a tag filter on any block. For example, I could add a page and add a forum block, but filter by a particular tag. I have a sports site and I could then create a page for each player, and put on a block that shows the forums posts, pictures, videos, related to that player.
I can actually hack up a page like this using the RSS feed, but it would be so much easier if you just added a tag field on all content blocks.
In fact, I'd love for you to do two things to take this even further:
1) Allow us to add a custom field to a blog/forum post/video/image, with a select field to make it easier to categorise content
2) Allow us to then user tags/custom fields to create dynamic pages ie URL/players/tag=John+Smith where by the tag would then be passed to the blocks so they are dynamically generated.
Ning as a CMS is very limited because of the lack of ability to categorise and use those categorisations - and its a shame because all the great web paging tools you now have (including the Landing Page editor) would be so much more powerful if you added these basic CMS features.
Please consider it, because having a great content set is of little use if we can't categorise it and use these categorisations to create new ways of displaying our content.
P.S. if there is a Ning developer there that has done something like this before (I imagine using HTML blocks pulling in an RSS feed) please get in touch,