Topher

Provides a user interface under the Reading Settings page for choosing what post element to orderby. Also allows the site owner to chose ASCending or DESCending.
NOTE: Does not allow for arbitrary ordering via drag and drop. This is a simple setting.
<h3>Usage</h3>
Once it’s installed, go to Settings -> Reading section, scroll to the bottom, and choose an orderby and order option.

Default Post Sort

I'm glad I came across this plugin. It does exactly what the title says and nothing more which is what I want in a plugin. 

Simple and straightforward. Great plugin.

Provides a user interface for setting a default post order.

oltdev

This is a simple plugin that enables users to modify the order in which posts are displayed on all pages(or in selected categories) of the blog. This is very useful when 
you have a blog in which you want to display posts in the order they were posted, from the first post being the oldest one, to the last post which 
is the most recent one, or the other way around. The options provided with the plugin at this moment allow users to order the displayed posts by post date, post title, 
post author, last time modified and post slug, either ascending or descending.
These post display options can be set by accessing the “Manage->Custom Post Order” link, for wp2.6, and “Tools->Custom Post Order” link, for wp2.7.

Custom Post Order

descending , posts, categories, wordpress mu, wpmu Requires at least: 2.6 Tested up to: 2.7 Stable tag: trunk The plugin enables any user to modify t …

Default Post Sort vs Custom Post Order