I just released the second feature that is now part of the Trentacular SharePoint 2007 Features CodePlex project: Central Administration Extensions
The solution currently deploys just a single custom action and page for managing farm properties. This has proved useful for us as a means to centralize configuration that is applicable across our entire SharePoint farm, for sale such as custom application connection strings, log4net config file location, etc.
If you are a seasoned ASP.Net developer, you may also find the included Delegate Data Source useful. It essentially exposes the 4 main data source methods (select, insert, update, and delete) as events that can be handled directly in your code behind.