I have been recommending Constant Contact as a great source for email marketing for several years now. In addition to lots of nice templates and a great learning center, they really make it easy for you to manage and keep up-to-date your email mailing list.
Since an astounding 85% of all email that is sent today is spam (original statistic from Cisco IronPort Threat Operations Center 2011), filtering for spam email has also become much more sophisticated. It is important to comply with the CAN-SPAM guidelines or your mail will not be delivered to your customers, and you may even be blacklisted by major mail services. Constant Contact helps you keep in compliance and takes care of the sending for you. They also have event registration and customer surveys as well.
With the rise of social media, they have put together another great resource for business owners. It goes over the basics of using Twitter, Facebook, LinkedIn, YouTube, and more to help develop your customer relationships. Find the site at www.socialquickstarter.com.
As a business owner short on time, I can appreciate how they have broken the guides into manageable segments and even let you pick the level of detail you’d like on each by letting you know how much it will take to review each topic.