The most important features of email list management tools are the ability to manage unsubscribes so your emails are CAN SPAM compliant, tools that make email design and setup quick and easy, and detailed analytics that give you specifics on the number of emails delivered, opened, links clicked on, and list management actions (unsubscribes, etc.).

For small businesses with small budgets and less technical knowledge, iContact is an excellent "starter" email list management resource.  At the low end, it costs only $30 per month, but has lots of easy-to-use options for customization, list segmentation and email setup.  It also offers tools to check the likelihood your emails will be flagged as spam based on their parameters, surveys, email design, tracks the "life" of your email lists, and of course manages unsubscribes.

For those with eCommerce sites, Aweber offers all of the above features, also at minimal cost, and adds the ability to integrate with ZenCart, a commonly used open source eCommerce site platform, to export customer information for use in email lists.

Another option I have heard good things about is MailChimp, which lets you store up to 500 contacts and send 3,000 emails a month for free, and also integrates with WordPress, Twitter and has geolocation tools that let you set delivery options according to local time, target physical locations, translate emails to local languages, and more.

There are many options now availiable for email list management, and the most important things to keep in mind when comparing/evaluating them are:

1.  Cost – some charge based on the number of subscribers on your lists, some charge based on the total number of emails you send per month, and others will offer you a flat rate with fixed numbers of each.  To evaluate the best solution for you, you will need to know how many email addresses will be on your list and how many emails you plan to send each month.

2.  Capacity – will limit the number of subscribers on your list, others will limit the number of emails you can send out each month, and some may limit how many you can send out at one time.  If you expect your list to grow and plan to increase the frequency with which you communicate with your list, make sure you understand where the capacity limits are and what the consequences are for exceeding them, so you won't be surprised by unexpected overage charges.

3.  Commitment – some providers give you service on a month-to-month basis, while others require a one-year or other commitment.  Before you sign up, make sure you understand what exactly you are signing up for.

4.  Customization – perhaps the biggest unforeseen issue with email list managers is whether and how they can handle any customization you want.  Most of the mainstream resources won't give you the ability to do everything in your emails that you see in emails you receive, so be sure to confirm your choice will allow you to include the functionality you want.  Interactive forms and Flash animation are not usually included, for example, so if you're not sure whether an email list manager will do what you want, check with the vendor before making your decision.

5.  Cancellation – if you plan to use a 3rd party vendor to manage your mailing list, make sure you know under what circumstances you can cancel your subscription, and what happens to your data if you do.  You should be able to easily export all of your data if you decide to change providers, but you will want to make sure that is the case and that  your data will be in a format you can use.  Also check on how to store the history of your email marketing campaigns outside of the list manager, so that information is also available to you if you cancel.