When you subscribe to another user, that user's profile will be listed in your subscriptions page. This also applies to subscribing to other users activities such as blogs etc.

From the bottom menu click on the little Gear icon (Settings Icon) and click Account Settings. You will be able to edit your profile details such as Headline, Description, Gender etc.

Go to the person's page that you want to block and look on the left hand navigation links for BLOCK.