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This plugin adds a drop-down list with the ability to sort your blog posts: 
* sort by title; 
* sort by date (newest first); 
* sort by date (oldest first); 
* sort by date last modified.
Paste the following code in the templates ‘index.php’, ‘archive.php’, ‘category.php’ or/and ‘author.php’ etc.:
This tag must be before The Loop. For more information go to the “Installation”.

WP Sort Posts

Add the ability to sort the posts in the archives of your blog!

LordPretender

This plugin adds a drop-down list with the ability to sort your blog posts :
<ul>
<li>by title</li>
<li>by date (newest to oldest)</li>
<li>by date (oldest to newest)</li>
<li>sort by date last modified</li>
<li>randomly</li>
</ul>
You can find a demo here : http://www.spoils.fr/ 
The widget is named “Trier les articles” on the sidebar.
<h3>Configuration</h3>
<ul>
<li>Widget title: the title of the widget</li>
<li>3 checkboxes in order to display or not items in the drop-down list.</li>
</ul>
Since the version 2.0.0, it is now possible to change the default order for your categories. 
In the category editing page, you will now find a dropdown list.

Posts Order Widget

Add the ability to sort the posts by context rather than descending date.

WP Sort Posts vs Posts Order Widget