Add a note about commands and cron tasks to the README

README.md

@@ -105,6 +105,22 @@ At this point, Django should run correctly:
     python manage.py runserver
 
 
+Available commands
+==================
+
+Some useful administration commands are available via `manage.py`.
+
+`python manage.py members_email`: returns email addresses of all members, one
+per line.  This may be useful to automatically feed a mailing list software.
+Note that membership is based on the `status` field of users, not on
+membership fees.  That is, even if a member has forgot to renew his or her
+membership fee, his or her address will still show up in this list.
+
+`python manage.py charge_subscriptions`: generate invoices (including a
+PDF version) for each subscriber.  You probably want to run this command
+every month as a cron task, see below.
+
+
 Configuration
 =============
 
@@ -125,6 +141,15 @@ in the admin.  Information entered in this application has two purposes:
 Some bits of configuration are done in `settings.py`: LDAP branches, RSS feeds
 to display on the home page, and so on.
 
+Cron tasks
+----------
+
+You may want to run cron jobs for repetitive tasks.
+
+To generate invoices on the first day of each month, here at 3 am:
+
+`0 3 1 * * /home/coin/venv/bin/python manage.py charge_subscriptions`
+
 
 More information
 ================