Nucleus is a blog software and a rather useful one, too. I use it for my front page.
It's rather easy to add extra functionality to Nucleus by writing plugins. Here you can find plugins I've written. If you want to see more plugins, go take a look at the Plugin page at the Nucleus Wiki.
As far as I know, it's not possible to print out the category description from a template. There's a skinvar (<%category(desc)%>), but no template variable to do the trick. Why did I need that? Because category names are rather restricted: I can't use Scandinavian characters in the category names. Descriptions have no such restrictions.
See it in action: Melankolia.net.
How to use it: Just add <%CatDesc%> on any template and it will print out the category description of the category related to the current item.
I wasn't completely satisfied with TopRated, so I improved it. My version uses SQL more efficiently (doing sorting and limiting with SQL). In addition to specifying the amount of articles to show, you can also choose to show the articles with the best or the worst ratings.
See it in action: Melankolia.net.
How to use it: Just add <%MostKarma(n,sort)%> on your blog skin. Replace n with the number of articles you want to show (default is five) and sort with either 'asc' or 'desc' (without the quotes) depending on if you want ascending or descending sorting (default is desc, ie. the best articles).
If you use my plugins and have any comments, send me e-mail at msaari@iki.fi. Also, if you drop me an e-mail with your blog URL, I'll add it to the list of blogs that use my plugins.