Razesdark

This plugin will allow all authors to have their own tweets shown on in the widget area of their posts, by adding it to their profiles. 
That way any multi-author blog can let their bloggers promote their own twitter account and not a joint account.

Author Based Twitter Widget

A Author based twitter widget, made to help multi author blogs have individual twitter widgets for their authors.

Maxaud

This plugin adds a menu item to the admin bar that reads “Collaborate” that when clicked launches a TogetherJS instance.
There are various settings that allow you to configure the TogetherJS options to your liking.
Let me know what you would like to see in future versions.
What other functionality should be implemented to help you collaborate with others?

Collaboration

A collaboration tool to integrate TogetherJS in to WordPress.

Author Based Twitter Widget vs Collaboration