I've been looking for a plugin to do subscription by email. Skippy's subscribe2, currently at version 2.2.2, is indeed very popular and I have activated that at my test ground here. I have yet to learn how to customize the subscription confirmation page.
There is another version allegedly an improvement using AJAX by Kirill. A not so popular one called "WordPress Email Notification Plugin" is here.
I don't know which is best I guess I have to try them out one by one.