We need to be able to collect our site visitors e-mail address to be able to send them newsletters, we cannot seem to find a sidebar widget for this purpose,
You can set up a contact page and request that readers who wish to receive your newsletter use it to subscribe. http://en.support.wordpress.com/contact-form/
You can set up email subscriptions so subscribers receive your posts by email http://en.support.wordpress.com/widgets/follow-blog-widget/
Your site stats page displays how many followers you have, who your followers are, as well as how many people are subscribed to post comments on your site.
Dashboard > Site stats > Total, 'Followers' , Shares
Click "blog" and when that page opens click "email followers"
Note 1: You cannot obtain any information that personally identifies any of your followers. This is a privacy issue. What's required for registering here is an email address only. That email address is for many of us a throwaway email address.
Note 2: This may sound "heavy" but I think it's important to recognize that when an email address is provided for a specific purpose, such as for receiving posts from a blog or submitting a comment to a blog, that is the only purpose it is being provided for, and any additional use of it is unauthorized. In Canada it's illegal to use an email address for any purpose other than the specific purpose it was provided for.