There is an approach without using widgets. It can be used to get a newsletter signup form.

You can try the code in this article:
http://www.techlila.com/how-to-add-newsletter-signup-box-genesis/

It will not work as it is. You will need to make one change.

The author of the techlila site has added this code at the end of the function:

add_action ( 'genesis_after_post_content', 'add_newsletter_box', 10, 1);

You will need to replace this line by:

add_action ( ''genesis_after_entry_content'', 'add_newsletter_box', 10, 1);

As far as I have understood, the hook name changed in the latest version of Genesis.

What I am sure of is that it works in Genesis 2.0.