In the rush to embrace new technology and new ways of communicating we often abandon the well established communication methods that people are used too. For example, people know how to use email. Everyone from grandparents to little children use email. It is still one of the most used services on the Internet and probably will be for a very long time, even with the problems of spam.
With that in mind it can be a very useful promotion device to still provide people with an easy method to forward your website information to their friends, family and coworkers by email. This blog for example has an email this icon and link on every post so people can quickly send the link to others. On other blogs I help with or publish the email this link is used quite often, and from the statistics email referrers account for just over 1% of the incoming traffic.
Another email option that you can provide, if you have an rss feed, is the ability for people to subscribe to your rss feed be email. This weblog uses Feedburner for that feature, but there are other services out there that provide that service as well. People that subscribe by email are sent an email archive of the latest posts from your blog once a day. This allows them to read the latest posts from your weblog with very little effort.
Website promotion by email is still a very useful tool to provide your visitors. It gives them an easy way to spread the word about your website to others, and is a great method to stay in touch with your regular visitors.