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

This module is basically the Drupal 7 successor to CCK 3's Multigroup in Drupal 6. A similar module is the Inline Entity Form. Caution: ...

Let's you create, edit, and delete entity references from any form that includes an entity reference field.

This module might not work well with translation and workbench moderation.

Also see Field Collection

From the project page: "Simplify allows particular fields to be hidden from the user interface. This helps to de-clutter forms and present a more user-friendly experience to content editors..."

The message stack of module provides the a great way to create a highly customized messaging and notification system

The htmLawed module enables the use of the htmLawed(X)HTML filter/purifier with text/input formats.

This module lets you use very fine grained html filtering.

See /docs/common-htmlawed-settings for common settings.

This module gives you an API to create search facets; integrates with the Search API module.

"This project implements code to make Drupal's configuration (settings.php) environment-dependent, so that you can have different sets of configurations in dev, staging and production. "

Rabbit Hole is a module that adds the ability to control what should happen when an entity is being viewed at its own page.

Also see Internal Nodes

Date Popup Authored provides a jQuery UI datepicker for the Authored on date field found on node submission forms.