To have email sent out whenever cards in a particular set are added, configure "send" in the card's rules. By default, it will be a Pointer to "|that set|+email config", which you can then fill out with who the email should go to, its subject and message, etc.
Let's say you want to configure an email to go out whenever someone adds an Event, with some event details. You'd go to Event's rules (under avanced in the menu):
Add EventFort Collins+Wiki Wednesdayportland+Wiki WednesdayBarCampPortlandBeaverBarCampGoogle Summer of CodeImminentChangesCampPortlandBarCampRecentChangesCamptest-Free Press
There, you scroll down and click the radio button labelled 'All "event" cards' and Submit. You can then click to add an email configuration. See the example above.
The purpose of the *from, *to, *cc, and *bcc plus cards is, naturally, to produce a list of email addresses. This can be done in a number of ways:
When emails are sent, all configuration cards are restricted to the permissions of the user who last configured them. So that, even though most users cannot view +*email cards, an administrator can configure an email to use such cards, and then any user with permission to create the triggering card will be able to email to those users.
If you don't want these emails to be visible to end users, you can use the *bcc setting.
You can use contextual names to further customize your emails. Within each email configuration card, "_self" will be treated as referring to the card triggering the email. See +*subject and +*message in the example.