Today I made a quick module for Joomla 1.5 to display a newsletter sign up box on your site. It connects with your AWeber account and signs up subscribers.
I looked around and found that a module was made for mambo but never updated. There was a plugin for $30 that also used the registration form, but all my client needed was a simple 'name', 'email', 'submit' type box.
So I updated the module to use css rather than tables, closed a few tags and added a few options. The css is all updateable from the module parameters, rather than having to root through your site to edit files.
You can see the demo and download it for free here
And you can read more about AWebers services here