Yello,
It seems to me that we could do with a newsletter signup upon registration. I want Mailchimp, but I'm sure there would be others that would like Campaign Monitor, Get App, AWebber, and the others that are about. I'm sure Mailchimp would be fine to start with. In fact a Mailchimp integration would be nice, although not a login type of product, it certainly would be a useful tool, I'm not sure all of the others out there meet the mark, there's so much scope, and there's an API available.