Amy,
Our office uses MailChimp (
www.mailchimp.com) for all of our newsletters, notices, etc. It lets you track openings, is free, and is fantastic! We've even been able to incorporate surveys or attach documents to our mailers. We will usually write a summary of the newsletter in MailChimp and attach a PDF that includes the full newsletter.
Takes some playing around to get used to. Definitely send out test mails to a select group before the real thing.
Hope this helps!