Where/how to save global variables?
Creating custom tokens is fairly easy in CiviCRM.

I would create a Group in CiviCRM containing the contacts of all the Board Members. By using a Group, as the Board Members change and are updated in the Group the token will automatically reflect the changes.

Then I would program a custom token that converts {board_members} to a list of the names of the contacts in the Group (separated with &lt;br /&gt;).

The link in @Ramesh's answer should help.

You could probably kludge together a solution using templates or something similar, but it is probably more likely to break and more difficult to upkeep.