We use Microsoft's ListBuilder service and MS-Publisher with a free ListBuilder add-in for a speedy creation and upload. You can upload any HTML source. We've learned lessons along the way (meaning it's not as seamless as they say it can be), but even incorporate some affiliate marketing in each issue with HTML code fragments.

Advantages we see are:

1) They manage the email list, subscriptions, and delivery on their servers. We upload the lists and can add/subtract as needed.
2) Users can subscribe/unsubscribe without us.
3) We send double opt-in invites through ListBuilder, i.e., they want to be on our list.
4) We can send targeted, segmented mailings based on the user subscription sign-up "survey" and "profile".
5) We can employ tracking to see who is interested in what.

There are others that do some/all of the above. We liked the simplicity and control of ListBuilder.

P.