Maybe if you hear what we did for a government agency, you may get an idea.
We used a Simplenews effectively and modified it with the aid of five modules.
They needed to include four content types from several different sections of the website out in a bi-monthly newsletter
They also wanted to reorganize them into two distinct newsletters that uses could subscribe to.
The four content types were publications, funding opportunities podcast and the site blog.
The blog had five distinct categories (taxonomy terms), for the sake of this discussion we will call them category one through category five.
For the form:
In order to reference nodes, you need the node reference field which is part of CCK in Drupal 6
(For Drupal 7 use References - http://drupal.org/project/references)
We created a newsletter content type that had eight different node reference fields.
The first node reference field was set to only reference the publication content type.
The second was set for funding opportunities content type and the third was set for podcast content type
The last five were set for the blog content type, but I needed to narrow down the selection of each of the fields so that one only showed posts tagged with category one, another showed posts tagged with only category two and so on.
To do this, we used the Node Reference views module. http://drupal.org/project/nodereference_views
(Reference views for Drupal 7 - http://drupal.org/project/reference_views)
Node Reference views lets you create a specific view and then you can use that view to filter out the node reference options for a specific node reference field.
In order to control the way the output of the different node reference fields looked, we used the Viewfeild module - http://drupal.org/project/viewfield. Once installed, you can choose viewfeild from the display options and then customize the view the way you want.
To control the rest of the newsletter, we used simplenews template - http://drupal.org/project/simplenews_template . It lets you add multiple newsletters with customizatible headers and footers, and the ability for users to pick between them.
To futher customize the display of each newsletter, we used Contemplate - http://drupal.org/project/contemplate modules for Drupal 6
(I would really recommend using Display Suite - http://drupal.org/project/ds for Drupal 7)
Lastly, if you need help configuring all this stuff, there are plenty of awesome video tutorials over the net.
Hope you find this useful and let me know if you need any further clarification.