Encouragement: I encourage all Drupal administrators to enable this module. Keeping you modules current is the first step to staying secure.
Description: - http://drupal.org/project/update_status
The "update status" module checks with drupal.org once a day to see if there are new officially released versions of Drupal and any modules that you are running. It requires cron to do its thing, so make sure that you have cron correctly enabled or it won't be able to know.
Status:
Pre-installed on Drupal 5 Resource Center websites.
Configuration:
Standard enable module: visit administer >> site building >> modules and enable this module.
Once enabled you can view available updates: http://drupal5.cei.psu.edu/admin/logs/updates