You can publish your notebook for all people, or share it with the limited number of people either by read-only or full access.
Go to "Sharing" page of the notebook:
If you click "Publish", your notebook will become visible to all visitors of the service. This article is a sample of published notebook.
If you click share, you will be asked for other users' e-mails. When you enter them, they will get invitations to view or edit your notebook. You can later revoke this access if you need.
You can also view all changes they made in the notebook history.
Please note that due to the distributed nature of shared servers sharing and collaboration is available at dedicated servers only.