Taxonomy Defaults allows you to assign default terms from any vocabulary to any node-type. The default terms will be pre-selected on the /node/add form, but can be edited.
If a vocabulary is marked as "Hidden" for a particular content type, then that vocabulary will not be shown on the /node/add form and the default terms will be assigned automatically and cannot be edited.
Taxonomy Defaults will NOT be ported to Drupal 7, as the addition of fields in core has made most of this module unnecessary. Discussion of D6 to D7 upgrade paths is happening here:
Versions 5.x and 6.x-1.0 of this module are only minimally supported at this time. You are encouraged to use the most recent release.