MOSS 2007 :Feature Stapling

A very interesting concept I came across is Feature Stapling.MSDN explains it as:

In Windows SharePoint Services 2.0, many of the customizations that organizations wanted required changes to the built-in site definitions. These types of customization were not supported by Microsoft because these files may need to be replaced by future service packs. To work around this limitation with the site definitions, you would copy the built-in definitions, make the required customizations, and hide the original definitions from the end user. This process would ensure that a service pack would not break the site definition.
In SharePoint Server 2007, Features enable you to turn functionality on and off within a site, even if the functionality was not in the original site definition. Although modifying the built-in site definitions is still not advisable or supported, you can use a process named Feature Stapling to attach a Feature to a site definition without modifying it in any way. For example, you can use this process to attach your custom application to the built-in definition.
For more refer:
http://msdn.microsoft.com/en-us/library/bb954662.aspx
http://blogs.msdn.com/cjohnson/archive/2006/11/01/feature-stapling-in-wss-v3.aspx

http://blogs.msdn.com/sharepoint/archive/2007/03/22/customizing-moss-2007-my-sites-within-the-enterprise.aspx