I get a LOT of e-newsletters but there are only a few I actually read. This small list includes Jeevan's BK Communique, which I wrote about the other day, but another comes from Blue Penguin Development's Michael Katz, who coincidentally helps people learn how to write these things.
Michael really understands the secret of a great e-letter, which is - in a nutshell - to claim your reader's immediate attention by focusing on what THEY want to know, rather than what you want to tell them.
Cultivating a distinctive personal style that's aligned with your purpose, as Michael does, is also important to e-marketing success. Plus he's absolutely hilarious, which never hurts.
Michael has been a guide to me for many years now, and if you're thinking of starting an e-letter of any kind (and imho keeping in regular contact with your audience is essential to any successful communications strategy), I can't recommend anyone better to study and learn from.