We use industry-standard for about a small portion of site development projects we undertake. Many clients already are familiar with this solution and wish to standardize with it. Smaller sites maintained by a handful of people are best for this solution.
Joomla is powerful open-source (free) software that enables clients to maintain and edit their sites via web browser. You can see a demo of Joomla, at our test site, by clicking here. Joomla is fully editable: any feature or customization you require can be installed by us or customized by our programmers. From registration systems to e-commerce, from provider directories to job boards, Joomla extensions allow clients the ability to extend their site for a very reasonable development cost. Joomla stores your site's information in a PHP database, so templates (designs) can be changed quickly, without redoing the site! This includes the navigation buttons and links as well – something not found in 99% of the proprietary CMS solutions available from other providers.
Another world-class robust CMS, Drupal has a different structure than Joomla, and fewer commercial extensions, but is easier to develop custom solutions for.
WordPress is a blogging platform that can serve as a CMS for clients who's business supports a blog-type format. It's especially good for smaller sites. With a base of more than 10,000 extensions, it offers an affordable path to CMS for many clients.
Web-based CMS offers a step up into the CMS world. Not as robust as any of the previous CMS platforms, it is the most affordable, easiest-to-use but least extensible CMS option.