I made a new MediaWiki extension, called Data Extension. Its meta page is at http://meta.wikimedia.org/wiki/Data_Extension and you can see it in action at http://www.rastko.net/~nikola/ .
The extension enables getting and setting data in articles, with some neat possible uses. It offers the solution for making sorted lists and an alternative solution to mass article import. To give an example, in an article on Paris, you could:
<setdata> is a=city population=2144700 is in=France </setdata>
which would write the data in the database. And then in Template:City you could have:
Population: {{#data:population}}
which would display it, and the List of cities of France by population could look like this:
<data condition="is a=city and is in=france"> * [[{{#data:}}]] ({{#data:population}}) {{#sort:{{#data:population}}|desc}} </data>
It is somewhat redudant with Semantic MediaWiki, because I didn't knew that it was so developed while writing it. But I think it also offers some things SMW doesn't have.