Counts articles in a WikiProject, and creates an edit button to change the number in the project page (you might have to add an XSS exception).
Example usage :
http://tools.wmflabs.org/magnustools/update_article_counter.php?language=de&project=wikipedia&page=Portal:Eifel
The page must contain a tag like this:
<span name='articlecount' category='Eifel'>1476</span>