John

This plugin enables you to manage your projects from the WordPress interface you are already comfortable with. Easily create and track the progress of projects and tasks.

WP-Trac

This plugin allows users to manage projects and tasks.

SherkSpear

This plugin creates Smart ToDo post types, todos are broken into tasks and categorized as Projects. Timers are added on each tasks.
Created Projects as taxonomy for Smart ToDo post types. And each Smart ToDo post types is capable of adding multiple tasks with url references.
Timers are provided on each task and can be controlled with buttons to Start, Pause and setting task as Done. Also edit buttons are provided to edit task description, task url reference and time spent. Proper user’s access are also given to each type of users.
SmartToDos manage page has columns for Projects and Status of the ToDo if it’s Open or already Closed.
Total hours are provided dynamically and Title of window is set to active task with the current time spent. This is inspired from the Task Timer Google Chrome App.
You can email me directly for any plugin request or personal modification such as styles and templates at <a href="mailto:contact@sherkspear.com" rel="nofollow ugc">contact@sherkspear.com</a> or contact me at <a href="http://sherkspear.com/contact" rel="nofollow ugc">http://sherkspear.com/contact</a>
Plugin URI: <a href="http://www.sherkspear.com/portfolio-item/smart-todo-wordpress-plugin/" rel="nofollow ugc">http://www.sherkspear.com/portfolio-item/smart-todo-wordpress-plugin/</a> 
Demo Page: <a href="http://www.sherkspear.com/smart_todo/add-pages-to-sherkspear-for-plugins-as-portfolio/" rel="nofollow ugc">http://www.sherkspear.com/smart_todo/add-pages-to-sherkspear-for-plugins-as-portfolio/</a>
<h3>Detailed Instruction</h3>
After installing the plugin you will find 
Detailed instruction at 
Dashboard-> SmartToDos->How To Use 
 /wp-admin/edit.php?post_type=smart_todo&page=smarttodo_info

Smart ToDo Plugin

This plugin creates Smart ToDo post types, todos are broken into tasks and categorized as Projects. Timers are added on each tasks.

WP-Trac vs Smart ToDo Plugin