You can add additional fields to contact's page using Centrium custom fields.
To define custom fields, go to Application settings and select "Custom fields" tab, or follow this url:

New contact custom fields can describe companies or people or both.

You can filter the contact list by content of selected custom field.

Custom fields that you added appear on add/edit forms of contacts and in the right column of contact's page.

Deleting custom fields will delete their contents from all records (contacts). This operation is not reversible.

You can also define custom fields for other entries in Centrium - tasks, deals and projects.