Moderating Revisions
There are certain "workflows" where you want pages to be created into a moderation queue, an admin approves them and they are published, the creator edits the page again, Drupal creates a revision, the original revision that got published stays published while the new edits are in a workflow for review/publishing.
Two modules attempt to achieve this feature and there's an issue to put the feature into core.
Revision Moderation: http://drupal.org/project/revision_moderation
- 6.x alpha and 5.x full release.
- 600+ users
Created to do specifically this. Has a great pedigree.
Revisioning: http://drupal.org/project/revisioning
- 6.x only (current official is 6.x-2.7).
- 600+ users on 6.x
Requires Module grants module. Has diff integration.
Groups:

