Some hints creating own plugins to CKEditor

Not a full guide but some helpful hints to get in the right direction.

Read this:
I've just checked the wysiwyg-geshi module, the integration with CKEditor module is not hard (but could be easier):

In ckeditor.config.js add something like:

config.extraPlugins += (config.extraPlugins ? ',geshi' : 'geshi' );<br />
CKEDITOR.plugins.addExternal('geshi', Drupal.settings.basePath + 'sites/all/modules/wysiwyg-geshi/ckeditor/');

and add selected buttons (Geshi-code, Geshi-php, ...) to selected toolbars.