A few days ago now Toolbar Buttons 0.4 was released. It contains a number of improvements so it is strongly recommended that you upgrade to it.
Some of the improvements include a few few buttons, support for both Firefox/Thunderbird 1.5 and 2. An options window and a patch for Thunderbird to allow added extra buttons to it. More about it Here
The Text Formatting Toolbar was removed from it though, you can still get it though in its own extension. The links in this post where added with it.