I use a variety of enewsetter campaign software for my clients.
Constant Contact only allows you to host under 10 pictures. That means every time you want to add a new picture for your newsletters or emails, you have to copy it to another program, copy the URL and then use that URL to link to the picture. Major pain.
iContact is much better and offers just about as many templates. Vertical Response is also a great one, that I use personally and is less expensive. The only thing I don't like about VR is that there is no undo button, so if you make a mistake, you have to log out quickly (before) your change is saved, and then log back in. VR also offers a LOT of great ideas about marketing in emails to their clients.
MailChimp is FREE - you might want to start out with this program if you're looking at doing your own campaigns, and then decide to make the leap to one of the other programs. Constant Contact is on the bottom of my list though.