I use MailChimp and love it because it's very professional looking. Here's one I did in December to give you an idea of what it looks like.
Subscribers receive an email newsletter that looks just like this, and they can even click on a link at the top of the email to take them to a webpage if they prefer. You can design your newsletter anyway you want (i.e., personalized header; different background, layout, pictures, fonts, colors).
If someone unsubscribes, you don't have to worry about it as MailChimp automatically does it for you. To get subscribers, MailChimp also allows you to personalize your own form to place on your website. I believe there are widgets too for WordPress and other bloggers.
You may have up to 2,000 subscribers for a free account. After that, they begin charging but it's minimal compared to some others I've seen.