Most DIY projects end up either saving time OR money; rarely both. Managing your own newsletter campaign, believe it or not, will save both of these precious resources.
Bockers & Pony (www.bockersandpony.com.au) recently saved a small fortune by managing their own newsletter marketing campaigns. There are really good email marketing tools available now, allowing non-technical users the ability to create professional, html newsletters with very little effort.
Typically to achieve this, clients would write their content, select some images, send them to their agency with a list of subscribers, and then have the campaign constructed and sent manually. The process of getting the content together, going back and forth with your agency a few times, run some tests, make some tweaks, etc, takes just as long as actually doing it yourself!
Tools like www.campaignmonitor.com and www.mailchimp.com allow the construction of these emails via an easy to use wysiwyg (what you see is what you get) editor. The systems also integrate seamlessly with just about any website, so all subscribers, etc are stored directly into the email system, rather than having to be imported each time you run a campaign. The unsubscribe functionality can also be integrated, meaning there is effectively no manual work required to manage your subscriber list.
You'll need to have an agency design, construct and test your email template once only, and you can then re-use that template over and over for each campaign you send out.
The cost of getting it setup right is typically about the same as having 2-3 campaigns sent by an agency - so you will recoup your costs very, very quickly, and create more flexibility about when you send your campaigns.