Review for Contacts Sidebar by throwawaylogin
Rated 5 out of 5 stars
Current releases can be found on the homepage. Version 1.7pre is compatible with Thunderbird 16.
Btw the check mark in the View|Layout menu is still inverted. It should be checked when the sidebar is visible, not when it's hidden.
To create your own collections, you must have a Mozilla Add-ons account.