Indie/small/medium-sized videogame studios with forums.
Alternatively, if you're not the sort of company that naturally engenders an active community, Twitter. It's not perfect, but it's a far better experience for customers who may want to keep up with what you're doing but don't want a new email to delete every week.
I'd really hate to be in the bulk email business today. Perhaps google will sell them back the data they used to create themselves.