If you are not sending out a monthly email newsletter to your clients I recommend:
1. Create 2 to 3 posts per week on your web site. So long as the site provides for RSS you can
2. Feed that RSS into Mailchimp and have it automatically create an email newsletter on a daily/weekly basis.
3. Don’t get hung up on creating the perfect content, perfect newsletter, perfect mailing list. They don’t exist.
4. Be consistent. Measure what’s working. Measure what’s not. Change.
Here’s an archive of the last 7 email newsletters that I generated from MailChimp. The last version (9/6/11) I updated the layout so that it looked a little more professional.
http://us2.campaign-archive2.com/home/?u=e818815686dc08f7eedd2931b&id=144a0927b1