RSSKey

The RSSKey module provides rss feeds for selected content (e.g. story or forum) and taxonomy, authenticated by a cryptographic key that is included in the feed url. This permits rss aggregators to get useful feeds from a drupal installation that does not allow
anonymous users to view content, or that varies content permitted by user.

The keys are unique to each user and site, and are based on an md5 hash of the user's password, and a site-specific secret.
Changing the site-specific secret changes all keys, invalidating any key-based urls previously in use by any user. A user changing
their password changes all of that user's keys only.

Feed urls are published to the Syndication module's page for listing.

This module requires the forms module at http://drupal.org/project/forms

A related module, actively developed, is http://drupal.org/project/tokenauth