adding functionality to the_content

I was wondering if someone has or will do a plugin for adding functionality to the_content as follows.

Say I have 2 different requirements for posts. One type of post goes to Articles (on one page) and another type of post goes to Blog (on another page). This is choosen via the Parent Categories.

Say Articles is cat ID 5 and Blog is cat ID 6 an each include sub catergories. Have the_content contain parameters to display specific categories only.

I.E.–
<?php the_content('excludecat=5'); ?>
to exclude articles from the blog page
and
<?php the_content('excludecat=6'); ?>
to exclude blogs from the articles page