GlassFrog lets you choose how frequently you receive email notifications.

To change your settings, go to Your Profile & Settings at the bottom of the main menu and click on the Notifications tab:

By default you will receive individual emails for the circles in which you are a member, but you can change that to only one email a day (daily digest) if you'd rather get fewer emails.

Then, you will be able to make changes to your notifications in each of your circles by selecting or un-selecting the check boxes. You can subscribe to Governance, Tactical and Role Note changes.