Blair Williams

Enables you to optionally push users to your <a href="http://aweber.com" title="AWeber" rel="nofollow ugc">AWeber</a> email list when they signup through mingle… This plugin requires you to also be running <a href="https://wordpress.org/extend/plugins/mingle" title="Mingle" rel="ugc">Mingle</a>.
<h4>See Mingle In Action!</h4>
If you’re wondering what Mingle is — it is another WordPress plugin that easily turns your wordpress blog into a social network. You can now try Mingle out in our Mingle Community! Come be my friend at:
<a href="http://wpmingle.com" title="Mingle WordPress Community" rel="nofollow ugc">Mingle WordPress Community</a>

Mingle AWeber Signup

Enables you to optionally push users to your AWeber email list when they signup through mingle... This plugin requires you to also be running Mingle.

Dave Doolin

Aweber Super Simple is a plugin that will subscribe a user whenever 
he/she registers to your blog.
The AWeber Super Simple options page allows you to configure the plugin to: 
* Choose whether or not to display the optin checkbox. Users may register if optin isn’t shown, and will not added to autoresponder. 
* Choose a checked or unchecked default status for the optin checkbox on registration. 
* Provide a custom optin greeting message for visitors
This code base is at least once, possibly 3, 3 or more times removed from what was the original 
code base. Wherever or whenever the ultimate source, the base code is old in WordPress years. 
Current effort is to bring everything up to 2.8 coding standards before attempting any extensions.
<h3>Support</h3>
Initial functionality will be supported on a time-available basis.
Installation, configuration and further programming support may be 
available on a contract basis. Contact author with request.

Aweber Super Simple

AWeber Super Simple allows you to subscribe users to an AWeber autoresponder when they register on your blog. NOTE: ALPHA VERSION.  Be careful.

Mingle AWeber Signup vs Aweber Super Simple