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Currently CiviCRM modules should contain their own user interface and are separate from the CiviCRM module itself. Eventually CiviCRM menus and and task lists will be extensible. If you would like to implement this type of extensible integration, please post you thoughts/design to the CRM-dev list.
Drupal Modules
To create and extension of CiviCRM, you will start with a basic drupal module. http://drupal.org/node/508
Use the CiviCRM APIs to access CiviCRM functionality. http://objectledge.org/confluence/display/CRM/CiviCRM+Public+APIs
Create your user interface for the module using the CiviCRM APIs
Example:
A Drupal module that allows export of a CiviCRM contributions search as a Quickbooks formatted export file.
1. Create the basic Drupal module
2. Implement search APIs (http://objectledge.org/confluence/display/CRM/Search+API%27s) and export APIs can someone provide a link to the export APIs?
3. Create your user interface for searching and selecting the records to export.
4. Create code to take the export data and put it in the Quickbooks format.
Joomla Modules
How do people create Joomla modules?
