Jon Tejnung

This plugin will give you three alternatives for managing your WordPress updates:
<ul>
<li>Update automatically – This updates WordPress/themes/plugins automatically and sends an email to the site admin when an update has been performed.</li>
<li>Update automatically (no email) – Same as the first alternative, but without the email.</li>
<li>Inform about updates once a week – This will send an email to the admin once a week if there are anything that can be updated.</li>
</ul>
Notice that only plugins/themes that resides in the WordPress 
repository will be updated/informed about.
The plugin has not been tested and is not primarily made for multi site-installations.

Simple Automatic Updates

Activate automatic updates or weekly notifications for the site.

kkarpieszuk

This plugin is for you if you don’t look inside of your Admin Panel every day (for example you have tens of wordpress installations) but still want to have wordpress up to date. After installation plugin will check every day if newer version of wordpress is available and if yes, will send email to blog’s admin with notification.

Upgrade Notification by Email

Sends daily notofication at admins' email if installation of Wordpress is out of date

Simple Automatic Updates vs Upgrade Notification by Email