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.

dreamsofmatter

This WordPress plugin is a complete flexible Projekt Task Management System. It helps you take control of all tasks when developing a WordPress Theme in a team or with a client.
Apart from common task management system features, Project Tasks have unique functions to link each task to a specific object in WordPress. And when you’re editing a page, it knows what objects and elements that page is made of.
Let’s say you have a page that uses the a certain page template, contains three different shortcodes and two different post types. When you create a project task on that page, these templates, shortcodes and posttypes comes up as suggestions to link your task to.
Project Tasks are accessable from the WordPress Adminbar when browsing your WordPress site where you can see how many and which tasks are linked to that particular page.
Project Tasks are also available from the the WordPress Admin that gives you an overview of all tasks and where you can manage them properly.

Project Tasks

This Wordpress plugin is a complete flexible Projekt Task Management System. It's a very easy to use, but yet a powerful plugin.

WP-Trac vs Project Tasks