It was announced a few weeks ago that would be upgrading their webmail service to be better, faster and include new and exciting features.
Launch day was put back due to complications getting the new service ported over.
To hinder this further, when they finally launched the new service it was slow and was unable to display emails for most of its customers.
The new webmail frontend is still being looked at, although you can login to it if you use the following url.

http://cpw.webmail.aol.com/

This will allow you to sign in and see the new features for yourself, which include web based AIM (AOL Instant Messenger) and a new calendar to new a few.
Have a look yourself.