What's the best way to manage a fan list?

One of the things that most people have figured out about online music is that it’s a great way to communicate directly with fans. If you collect their email addresses, or connect with them using some online social network or contact management system, you can send them stuff. Latest release information, links to videos, concert dates, news, photos and so on.

Better still, most of the time fans enter into these relationships willingly and voluntarily. They will happily write their name and email address onto your clipboard at a gig or fill in a short online form in exchange for an mp3 or video.

But what to send them, how much and how often?