1. They can click the "unsubscribe" link on the emails of the post they receive at the very bottom of the emails.

2. Or they can go here > http://wordpress.com/#!/read/edit/ and locate this:
"Get new posts by email" in the drop-down menu they have these choices:
never
instantly
daily
weekly

3. They can also click the "x" next to any blog there to unfollow it and no longer receive posts in their Reader or by email.

For trolls, you can “blacklist” them at Settings > Discussion toward the bottom of that page. Enter their email address, their username, and if they included it, their website. That will automatically send them to moderation so that their comments do not appear on the blog. Do note though that if they are determined, they can use a different email address or username to get around that. Also, do not put their IP address in the blacklist. IP addresses are no longer unique, and you might end up blocking legitimate visitors. Also, all they would have to do is go to a wi-fi hot spot, or connect via a different ISP and they could get around that.
http://en.support.wordpress.com/settings/discussion-settings/
http://en.support.wordpress.com/settings/discussion-settings/#comment-blacklist

One other thing I would suggest is to set your blog so that first time commenters are held in moderation till approved, then from that point forward they will not need approval. Settings > Discussion. The next step on that of course is to set it so that all comments are held in moderation until approved. That way you are in control, and they might just get tired and go elsewhere after a while.

how do I see a list of the people who are subscribed?

You can view your followers via this link http://wordpress.com/#!/my-stats/?blog_subscribers

Go to your site stats page and click “Totals, Followers & Shares”
Click the Blog link under the number and the Site Stats » My Followers page will open. Click the Email Followers link.
http://wordpress.com/#!/my-stats/
http://wordpress.com/#!/my-stats/?blog_subscribers
http://wordpress.com/#!/my-stats/?blog_subscribers&type=email

The subscriber stats on your site stats page show you all the users that have active email subscriptions to your blog using the built-in email notification system on WordPress.com. They don’t include users that subscribed using a third-party subscription service or using RSS.

P.S. You cannot obtain any information that personally identifies any of your followers. This is a privacy issue. What's required for registering here is an email address only and that email address is for many of us a throwaway email address.