Here’s a video that provides an overview of Modx. I believe this is pronounced, “Mod ex” and not “Mode ex” as in the video, but it’s still a great overview:

One thing that strikes me as great about the Modx CMS is that it seems really easy (as in, really really easy) to take a simple HTML + CSS website and turn it into a site with a content-management system without having to learn a lot of Modx.

Taking a website made out of HTML pages in turning it into a WordPress theme involves cutting-and-pasting code into several pages (header.php, footer.php, page.php, single.php, archives.php, and sidebar.php) whereas Modx has a page-to-template relationship.

That is, an HTML page corresponds to a Modx template, instead of being comprised of a header template, a footer template, a sidebar template and so on the way it can be with WordPress. This really speeds up the learning curve…

Another thing that stands out immediately with Modx is the way you can write web-standards HTML and CSS…waaay less HTML and CSS with a typical WordPress install. HTML markup on a Modx site can be very clean (basically, as clean as the front-end developer / web designer makes it)