Justin Tadlock

The Query Posts widget was written to allow users that don’t know their way around PHP to easily show posts in any way they’d like. It’s like having a cool WordPress developer as a friend ready to do your bidding. Seriously.
The widget has over 40 options to choose from. You can list posts by category, tag, custom taxonomies, author, date, time, name, or anything you can imagine. You can choose to show the full content, excerpts, or even a simple list. You can order the posts in all sorts of ways. Oh, and you can even show pages.
This is the widget that keeps users out of the code and gives them the ability to display items on their site how they want.

Query Posts

A WordPress widget that gives you unlimited control over showing posts and pages.

stiwahn

Simple Page to Sidebar is a plugin that adds a widget which enables you to display any page content in your sidebars. Just choose any page using the dropdown in the widget area. Also unpublished or private pages content can be shown.
<h4>Features</h4>
<ul>
<li>No posts, just pages.</li>
<li>Internationalized for english and german.</li>
</ul>

Simple Page to Sidebar

Simple Page to Sidebar lets you simply add page content to a sidebar. No more, no less.

Query Posts vs Simple Page to Sidebar