It took me forever to try and work out how to do this. Basically the problem is that you want to create a new console view in Eclipse for your plugin.

This is achieved by:

MessageConsole console = new MessageConsole("My Console", null);
ConsolePlugin.getDefault().getConsoleManager().addConsoles(new IConsole[]{ console });
MessageConsoleStream stream = console.newMessageStream();
stream.println("Hello, world!");

The third line is very important - without this, the console will not be added to the view. I got this idea from

(The book Official Eclipse 3.0 FAQs, which had FAQ 307: How do I write to the console from a plug-in?, was totally useless.)