What platform to use to build a how-to site with user content and moderation?

I have a CS education but consider myself a self-taught programmer (whoever said CS <i>taught</i> you programming!). I have a (novel :) idea for a how-to guide for a niche area that I feel has been largely ignored. Mainly original content, with an ad-based business model.<p>What platform and technologies would you recommend to get a site up and running quickly? I need an easy way to write articles, have other editors write articles AND allow users to submit/contribute to articles + comment. Small item, but also need directory structure to be hiearchical so that it appears like http://domain.com/category/topic/<p>I am comfortable with PHP, AJAX, CSS, etc. but would much prefer a turnkey system so I can get to producing content quickly and less time on coding. Considered Wordpress but feel that may not provide the required feature set...of course I may be wrong. Need something similar to what drives ehow.com, mahalo.com How-to's etc.<p>All ideas welcome, thanks.