Is it possible to allow someone to resubscribe to a list once they have unsubscribed? I see reference in the forums to "AddAndResubscribe" but I don't follow what it does or how to implement it.
If you use the default unsubscribe confirmation page, it has a resubscribe link built in. It's not currently possible to have that link on a custom unsubscribe confirmation though. You would need to just put a subscribe form there and have people sign up again.
The AddandResubscribe method is used by developers with the API - see http://www.campaignmonitor.com/api - for programmatically resubscribing people.