Wysiwyg

The WYSIWYG module is my favorite for rich text editing in Drupal 6 and Drupal 7. (In Drupal 8, WYSIWYG is in core.) Here's how I set it up.

Display Suite

Provides some advanced layout and display options for content. "Display Suite is a module that takes over the rendering of entities."

Field Conditional States

With the Field Conditional State module you can change the state of any supported fields form element depending on the content of other fields. This is done by providing an UI for Drupal's States API. All the changes made to a form by FCS (Field Conditional States) utilize only the States API and therefore are clientside only.