CalendarExport

CalendarExport is an addon that, with the in-game calendar open and an event selected will export the list of charactes that have signed up, the time they signed up, and their signup status (confirmed, tentative, etc).

With the in-game calendar open to an event with signups, you can click the minimap button or type /calexp to pop open a window that will allow you to copy the given text and then paste it into another document for manipulation.