Migrate

About

The Migrate module provides a flexible framework for migrating content into Drupal from other sources (e.g., when converting a web site from another CMS to Drupal). Out-of-the-box, support for creating Drupal nodes, taxonomy terms, comments, and users are included. Plugins permit migration of other types of content. For more information, see the online documentation for the Migrate module.

Uses

Getting Started
To get started, enable the migrate_example module and browse to admin/content/migrate to see its dashboard. The code for this migration is in migrate_example/beer.inc (advanced examples are in wine.inc). Mimic that file in order to specify your own migrations.
Migrate Support
The Migrate module itself has support for migration into core objects. Some built-in support for migration involving contrib modules is in the migrate_extras module.
Migrate Extended Support
The best place to implement migration support for a contributed module is in that module, not in the Migrate or Migrate Extras modules. That way, the migration support is always self-consistent with the current module implementation - it is not practical for the migrate modules to keep up with changes to all other contrib modules.