Sent every day at noon, the daily email update lists additions in the last 24 hours (or over the weekend if it's Monday), including:

To start receiving the daily update, just go to your user preferences page and choose "yes" for the "receive daily update" option.
You're not logged in right now. To receive the daily update, you'll need to log in or register if you haven't already done so.

To stop receiving the daily updates, simple choose "no" for the "receive daily update" option in your site preferences. If you're unsure who you're signed up as, check the bottom of each update for details.