JIM MCGOWAN ToDo can indeed link to do items with contacts from Address Book. There are a several ways to do this.
The first is to simply drag a contact from Address Book's main window into the linked item field in ToDo's inspector window. The Second is to install the ToDo Address Book plugins (by selecting ToDo>Install Address Book Plugins from the menu bar). This allows you to click on a phone number or email address in Address Book and create a new call or email reminder item from the contextual menu. Finally, you can install the Quicksilver Plugin (ToDo>Install Quicksiver Plugin) and when you select a contact in Quicksilver there are actions to create contact reminders in ToDo.
A ToDo item that is linked with a contact will give you the option in the inspector to set a call reminder or a email reminder. If call reminder is selected, when you click on the open link arrow for that item a bezel is drawn onscreen with the telephone number in large type. If email is selected, clicking the open link arrow creates a new mail message addressed to the contact in your default mail client.