In case of a multilingual application, one might consider it a reasonable approach to store the preferred language of the user in a session variable, and after that, every time a page is requested, to check this session variable and render the page in the indicated language.
This tutorial shows a Yii-way of doing this.
We implement an event handler for the onBeginRequest event; as the name of the event suggests, this event handler will be called at the beginning of each request, so its a good place to check whether a language is provided (via post, session or cookie) and set the application language accordingly.
We also implement a simple Language-Selector Widget, which can render the language options as ajax-links or as a drop-down list.
In this tutorial will be explained a method to manage some configuration runtime. This excellent tutorial follows a similar approach, but requires to write a masterclass which all controllers are supposed to extend, following this wiki you can achieve the same by only editing the configuration.
Changing the way a CGridView is rendered from the configuration file, or through behaviors specified at the moment it is used, is handy to extend a CGridView without creating tons of different classes for it.
I am surprised that this is not in the default implementation, so I made my default CGridView implementation.
If you're working a lot with extensions you often stumble upon problems, when you want to include them into your custom web application, like hardcoded or absolute path aliases or classes extended from core application components, which implement addiditonal features.