Apple AddressBook, 
Outlook and OutlookExpress.
PerfectTablePlan can import guest information from vCard files. Many
types of application can export contact information in vCard format,
including personal organiser and email packages such as
Apple AddressBook,
Outlook and OutlookExpress.
To import guest information from a vCard file:
drag the vCard(s) files (extension .vcf) onto the 
Guests pane
or 
Groups pane;
or
select File|
Import,
choose vCard file
and click OK. Select
the vCard file to import and click Open
In some application (such as Apple AddressBook) you can even drag vCards direct from the application into the Guests or Groups pane.
PerfectTablePlan will attempt to preserve groups defined in the vCard. Guests in the same group will have their proximity set to 'near to'.
To change the group and proximity of imported guests:
bring the Groups
pane to the front
drag and drop couples/families/groups into the same group (you can rename the group if required)
right click on each group and set the appropriate proximity
delete the empty groups
See also:
Import guest details from the Apple Address Book