Just wanted to give a link back to our detailed article on email newsletter tools, if it's useful. It's
on TechSoup or there's an updated version
on the Idealware website
Just a word about looking for email newsletter solutions, particularly when looking at free options: you need to be careful that you don't get yourself blacklisted as a spammer. If you're sending lots of emails from your own servers, using something like a PHP script, you run the risk of having all your email addresses flagged as a spammer. This would mean that every email sent from your organization email addresses - not just your newsletter, but everything - would be trapped, and not make it through to the intended recipient. It's not very likely, but really bad if it happens - it can take weeks or months to get off the blacklists.
Unless you're quite familiar with what you're doing, it's likely best to go with a hosted option for that reason (ConstantContact, Intellicontact, GraphicMail which have been listed are all hosted, or see the article for more). In addition to the few free hosted options (GraphicMail, for instance), there are tons of options for $20 a month or so. $20 isn't much of an investment compared to jumping through a lot of hoops every time you need to send out an email newsletter....
Laura
www.idealware.org