iContact is an affordable (prices that start at $9.95 per month) solution for anyone who wants to send out email newsletters. They sport an extremely easy to use interface, numerous templates, with surveying, autoresponder, and blogging capability.
They take care of managing bounces and unsubscribes for you (this is a big perk if you have ever tried to manage this yourself like I have). They also take care of the backend technical details like making sure your message gets to the inbox of your recipients through their ISP relations, feedback loops, and whitelist status, etc.
The company has over 15,000 customers and 100,000 users. The product is used primarily by small businesses but also has a number of Fortune 500 companies like Bank of America, Ford, Nissan, Super 8 Motel, and International Paper, and political campaigns like Barack Obama '08.
You can download their free Best Practice Whitepaper on email marketing to get a better feel for the benefits of their tool. You can also view a video overview to learn more about their iContact Email Newsletter Tool.