Hi Tamara,
I use Aweber to manage my mailing lists, and they also have a feature called Blog Broadcaster - so visitors can sign up for email updates from my blog. You can also broadcast an email directly to that same list if you want. If you'd like to check out Aweber, our link is:
http://sswt.aweber.com
The reason I use them exclusively is because I OWN the email lists. If you set up a list or notification service anywhere else, be sure to find out if you own the list you are building. Whether you can make backups of that list, move that list, email that list directly, customize the opt-in and follow-up process, etc.