We use the MailChimp module coupled with a MailChimp account with great success.
Disadvantage: third-party and not free if your list is large.
Advantage: - mass emailing acan put a load on the server and harm site performance - you offload this to MC - it can set off spam filters, so you run the risk of having your site blacklisted - excellent opt out.
BTW - Brian Lewis interviewed maintainers of the most popular options on the Modules Unravelled podcast. I think he has a series of 4 interviews, about 45 mins each. When I was setting this up, it happened to coincide with a 4-hour drive and I found it a nice overview.