I created a simple plugin for YAML settings: Yettings
It works in a similar fashion to the code in khelll's answer, but you only need to add this YAML configuration file:
app/config/yetting.yml
The plugin dynamically creates a class that allows you to access the YML settings as class methods in your app like so:
Yetting.your_setting
Also, if you want to use multiple settings files with unique names, you can place them in a subdirectory inside app/config like this:
app/config/yettings/first.yml
app/config/yettings/second.yml
Then you can access the values like this:
FirstYetting.your_setting
SecondYetting.your_setting
It also provides you with default settings that can be overridden per environment. You can also use erb inside the yml file.