Sorting posts by number of hits? — and other confusions

Hello! This is my first time digging into WordPress. I have spent about a day reading the codex, and I’m starting to “get it” but there are naturally still a number of mysteries. I’m not looking for someone to do my work for me, but a nudge towards the right corner of the codex would be greatly appreciated.

I’m trying to return a feed of the most popular articles within a particular category in a sidebar.

From what I’ve read, it seems that I just have to do some “simple” magic with the loop and use #category to filter the feed… but how do I go about sorting by number of hits?

I’m beginning to guess that WordPress does not track this statistic out of the box. If it doesn’t, is there a good plugin that will make this easy for me?

Thanks!