Official comment

The easiest way for your example would be to add three custom fields to the Contact Record in Contacts >> Settings >> Field Editor:
Consultant Name (field type: text)
Consultant Email (field type: email)
Consultant Website (field type: text)
I don't know how you have your lists separated, but if they are in Groups, you can display the Group and then use Group Actions to prefill these fields for all of them. Display the Group and select "All in Group", then "Change Field" from the action bar across the top.
After you have filled the fields in all three of your Groups you can use merge fields in your emails for all three. The merge fields should be selected from the merge field drop down in the email editor. In the email they would look something like this:
[Consultant Name]
[Consultant Email]
[Consultant Website]
When ONTRAPORT creates the email it will pull the information from the individual Contact's Contact Record. If there's nothing in the field it will be blank. Putting the [Consultant Website] on the bottom ensures there's no gap between the other information (assuming every consultant has a name, some of them have an email, and fewer of them have a website).
I know sometimes people use a simple example for a more complex set up, and if that's the case here the solution may be different.