E-mail subscription for multisite

Hi everyone!

I have been looking (for some weeks already) for a plugin to give users a chance to subscribe (with e-mail address) a blog he wants in my WP3 multisite installation. I didn’t find any or then I’m just a bit blind ?? So is there such a plugin?

More details: I’d like to have a “subscribe” link on every sub-blog and the link would register automatically the e-mail address of the registered user to this specific sub-blog mailing list. Just any suggestion is welcome ??