This plugin provides users with a to-do list feature.
You can configure the plugin to have private to-do lists for each user or for all users to share a to-do list. The shared to-do list has a variety of settings available. You can assign tasks to a specific user and have only those tasks that were assigned viewable to a user. You can also assign different permission levels using capabilities.
A page is added under the Tools menu to manage items and they are also listed on a dashboard widget. You can manage the settings from under the Settings menu.
The plugin is a modified version of an abandoned plugin. I orginally just fixed it to work in WordPress 2.7 for my own use, but have since made many additional improvements.