Change the author of a node
The easiest way I think is this:


Install the views, views_bulk_operations, and admin_views modules.
Go to the content listing (admin/content).
Filter the results to get the nodes you are interested in.
Check the checkboxes next to the node (there is also an option to select all).
Select "Change author" from the operations dropdown and click the "Execute" button.
Select the user you want to change the author to and click the "Next" button.


Admin views uses views bulk operations to override the default drupal administration views with something a lot more useful.