SoftwareMarketingResource

This web site exists for many years and has improved immensely over time. From articles to referrals, if you are in the software industry, you can probably find something that's relevant to your business.

http://www.softwaremarketingresource.com/

UniSender

UniSender helps to deliver electronic newsletters quickly and without any additional software installation. The only you need is to upload your mailing list, create the message and hit "SEND" button. The rest will be done by UniSender within seconds.

http://www.unisender.com/

Constant Contact

If you would like to email a newsletter to your clients and having some trouble designing it, or you just don’t want to waste too much time on it, "Constant Contact" is what you are looking for. They offer a generous trial period and have one of the best customers support.

http://www.constantcontact.com/index.jsp

SuretyMail

If you want to distribute a newsletter by yourself and have issues with your delivery rate (assuming you're not a spammer) - "Suretymail" is probably what you're looking for. Their screening process is a bit of a pain because they have to make sure you won't damage their reputation, but once you've made it, these guys are worth every penny and they're actually more affordable than others according to our research.

http://www.suretymail.com/