Getting started with Eclipse plug-in development

If you decide to build your own Eclipse plug-in, you'll need 
 good documentation and development tools. Before you spend time 
 looking for documentation, I'd try the help built right into Eclipse.
 It includes the Platform Plug-in Developer Guide, the JDT Plug-in Developer Guide, and the PDE Guide, all searchable by keyword. The built-in help also links to the API documentation (Javadoc) for the runtime components. Another great resource is the Official Eclipse 3.0 FAQs (special thanks to ienik).

What better place to develop an Eclipse plug-in than in Eclipse itself? Eclipse provides 
 a dedicated set of tools called the Plug-in Development Environment (PDE). With PDE, 
 it was fairly easy for me to get the hang of writing my own extensions. A good place to start is
 PDE Does Plug-ins. Any Eclipse developer should also make time for Eclipse Corner Articles.