I am adding taxonomy subscriptions to a site and decided to document stuff here to help others achieve the same result. Please contribute your experience.

This process assumes you already have your taxonomy terms attached to content and will use some of those terms here.

1. Install the Subscriptions module. Download at http://drupal.org/project/subscriptions. Documentation at http://drupal.org/node/344030
2. Install the Taxonomy Subscriptions module, included in the Subscriptions package.
3. Open your Web site in Firefox and log in as Admin.
   • Visit Administration » Configuration » System » Subscriptions and set the Taxonomy settings.
     • You select vocabularies for inclusion.
     • You select vocabularies for exclusion.
     • I hope somebody adds an explanation of the difference.
   • Give authenticated users the permission Subscribe to taxonomy terms.
   • Open your Web site in Chrome and log in as your test user.
     • As the test user:
       1. Select My account.
       2. Select the Subscriptions tab.
       3. Select the Categories section.
       4. Subscribe to something.
       5. Test.

Taxonomy settings

By default, the user can subscribe to every term in every vocabulary until you select something in Taxonomy settings.

Omitted vocabularies

Select vocabularies here to reduce the length of the list in the user profile. You select the vocabularies you do not want to see. It is a multiple selection list and you can easily lose previous selections when changing the list.

In my current project, I want to select 5 vocabularies out of 30. Instead I have to select the 25 I do not want to appear in the list.

Restricted vocabularies

This had me confused. If you select a vocabulary here, the vocabulary name appears in the user selection options but without any terms. I think you have to select the terms you want to be visible. I did not explore this option. Please add your experience here if you use this option.

Subscribe buttons

You could add Subscribe to pages like this buttons. See http://drupal.org/node/344030#subscribe_links for the links to add to Subscribe buttons.

There are no examples of what you can do when a page is tagged with several terms.

How to subscribe for multiple terms

All subscriptions are independent. A or B or C. There is no A and B and C. See issue http://drupal.org/node/1652582. Perhaps a future version will have rules so we can use more complicated selections.

My project uses Workbench Moderation and fires an event when a node is moderated. I am looking at Rules to combine some selection criteria and send an email.

As a quick test, I edited and published a draft node. The node ended up in the subscriptions_queue table as two identical rows, probably the first from the node update then the second from the moderation change. Subscriptions removed the duplicate entry when sending the mail.

Function subscriptions_queue($event) looks like a function you could call from a rule to add an entry to a queue. Just need the function presented as an action. Bingo! Someone is already working on it. See http://drupal.org/node/876672 and http://drupal.org/sandbox/oliverhuynh/1591962.

There may be other modules you can combine here. Please add notes about anything that works for multiple selections.

Testing hints

Set your user subscriptions to As soon as possible to get a fast response to tests.

The email is sent in a cron run. Edit your content to change tags then run cron to pick up the change and send the email.