Easiest way to implement email subscriptions?

I’m looking for an easy way that a visitor can simply input their email address and then hit a button to subscribe to my blog posts. Similar to WordPress.com’s Blog Subscription Widget.

What is the easiest way to accomplish this?

I’ve checked out Subscribe2, and that seems to be pretty decent. But it only sends emails to users that are subscribers. I do not want users to have to sign up for an account on my blog just to subscribe. I want them to be able to simply input an email address and be done. My users for my site are not very computer literate so the easier it is the better.

What plugin(s) can help me get what I need here?