On PHPBuilder.com today there's a new article looking at working with the three Symfony component libraries as standalone tools that can be used outside of the framework - YAML handling, templating and an event dispatcher.
These libraries were once an integrated part of the Symfony project, but now they represent a separate Symfony project. Because the Symfony Components are standalone PHP classes, you can both use them without the Symfony MVC framework and integrate them very easily in any PHP project. You can install each of the Symfony Components in the same, very simple manner. All you need to do is download the source code (a TAR or a ZIP archive) from the project page.
The tutorial goes through each tool, briefly explaining what the technology is that's involved and provides some code examples to show you its use.