In the short term (i.e by Monday), your mailing list members will be "members" of your site. You will be have the option to make pages and features like the guestbook "members-only". You'll also be able to collect more information for your mailing list, including full name and address.
In the next 2 months, our goal is to make each of your sites a real "community"... like a mini myspace.com. Members of your site can have complete profiles with photos of themselves. You'll be able to see who's logged on, chat, and let other members know who's coming to your next show. Members will also get extra privileges like the ability to upload photos to your site and more. We'll keep you posted on our progress!