CKEditor is new favorite rich text editor however I prefer to use the WYSIWYG module because it seems to have better media module support. This module, however, is needed if you plan to use the Scald module. If unsure, then I suggest using the WYSIWYG module instead.

"The proposed HTML "picture" element (see responsiveimages.org, but has not been accepted for HTML 5) is implemented as a display formatter for image fields. This module is a backport of Drupal 8 picture module. This module will deliver alternate image sources based on device capabilities to prevent wasted bandwidth and optimize display for both screen and print. "

Here's how to customize CKEditor in Drupal 7. I recommend using the WYSIWYG module instead of the CKEditor module if you plan on having media module integration. I was not able to get media module working with youtube videos and CKEditor 4+ and apparently that's a known issue (Apr 26 2014).

This is how to create a plugin for CKEditor. I also show how to integrate it with the WYSIWYG module. It was tested on CKEditor 4.3.4 and the WYSIWYG module version 7.x-2.x-dev from 2014-Mar-20.

"Set JPG quality per image style
This module allows you to specify a custom quality on different image styles you create. After installing and enabling this module, you will have the option to add a new effect to your image styles, enabling you to change the quality."

"Defines a field type Block reference which allows the block to be displayed as the content of the field." Alternately, if the bean module is enabled, blocks can be referenced using the entity reference module instead.

Maintained by Dave Reid, Earl Miles, Damien McKenna and Derek Wright

Smart Trim implements a new field formatter for textfields (text, text_long, and text_with_summary, if you want to get technical) that improves upon the "Summary or Trimmed" formatter built into Drupal 7

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.

This module "allows permissions to be set to each field within the Authoring information and Publishing options field sets on the node form. It also allows selected field sets to be set as collapsed and / or collapsible."