Alex GetResponse is a good service too. They have a smaller customer base than MailChimp or Aweber but they are definitely on the right track. You should consider your own options that will help you decide. For example, pricing, growth, support, reliability, deliverability, spam filters, etc. Make a list of these factors to compare on your own, you will also find such analysis around the web but those analysis could be biased towards one of the service. So you better do it on your own.
I actually use both services today so I can keep this review up to date. Overall, I think Aweber has a better deliverability rate which is a huge reason to use them. Furthermore, i like the way they do autoresponders much better than MC. On the flip side, MC has a much easier to use API if you are into coding and manipulating your lists programmatically.
After you have entered your "List Name" you will need to enter a "List Description." Here is where you will describe the kind of information you'll be sending from this list. There is a 400 character limit for the "List Description." Subscribers will see your "List Description" on the unsubscribe page if they ever go to unsubscribe from your list. Once you are done entering your "List Description" click the "Next Step" button.