do-index custom blog description on category page

Hello all!

Hope for some help for this one:

I run WP2.9.2 and use the allInOne seo plugin. It disables indexing of my category pages in order to avoid duplicate content. However, for SEO purposes I would like to index my category page as well. My front page is a static page and my blog entries are not published to any specific page. They are linked to from the front page via a “recent posts” widget and you can also see them via the link to the category from the front page.

What I would like to do is: have the post pop up under “latest 10 entries” and then, in its category, add a custom description that is unique and doesn’t include anything from the blog entry itself.
Any ideas for what I can do?

Is there a widget for this? I couldn’t find one but I may have been searching for the wrong thing using the wrong keywords (wouldn’t be a first ;-).

Looking forward to your answers!