This is one of the most powerful extensions used. If you plan to migrate your site from a different CMS to eZ Publish, data import can be the solution for all of your questions. The purpose of the Data Import extension is to import data from a given data source (such as the xml/csv documents) into the eZ Publish content tree using an object-oriented approach. Developers need to implement a SourceHandler that understands the given datasource that is completely independent from the import operators. The import operators contain the logic of how to create/update the content nodes in eZ Publish.

You can download from http://ez.no/developer/contribs/import_export/data_import.