By default, Automattic’s phenomenal P2 theme does not support posting into categories from the front page, it only supports tags. My fork of the theme called P2 Categories does that though and lets you conveniently select a category from a drop down menu right there on the front page.
I wrote an update to it last week, and in so doing my article from 2013 came in handy that explains how to add this functionality to P2. Nothing much has changed in the source code, so it’s still relevant and accurate.
What the above article did not explain however was how to show which category a post belongs to. And because it’s still fresh in my memory how to do this, I thought I’d better write it down for next time (and anyone who’s interested in how to do it).