For me the best open source CMS is Drupal. I have used WordPress before and I can create my own blog site for free and I can choose a template, a widget, a theme, a rich plugin architecture and more. The downside is WordPress has security vulnerabilities compared to Drupal where security is rock hard solid and got loads of modules, theme engines, translations and other options to choose from.
Currently I'm reading a book on Textpattern CMS. I have seen high quality sites built with it. It is very flexible with its plugin system and also designer friendly because of its templating system. I have a good feeling around it.
An article on how to choose a web hosting service provider, read here.
Joomla is at the top with its vast number of extensions that enable developers to build a full featured web application in just hours. Some web hosting companies provides you with joomla installation which makes it more convenience..
With out a doubt WordPress is the best. I despise Joomla as its NOT a CMS. Its a bulked out portal. Regardless of what anyone says, its not been a CMS since day one. A CMS is simple, just manages content. Not articles, pages, sections, etc - just content.
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