Bookmarks' Full Titles version 2.0 is a tiny extension for Firefox 2 that eliminates truncation of bookmarks' titles, in the Bookmarks menu and in dropdown menus from the Bookmarks Toolbar.
If you're using Firefox 3, you want Places’ Full Titles instead.
Bookmarks in top level menus - i.e. directly under the Bookmarks menu or directly under a folder on the Bookmarks Toolbar - don't expand to full width, because submenus would be inaccessible if they did. But this extension does make them somewhat wider than they are usually.
It was inspired by some code _Jim_ posted to MozillaZine Forums that I then packaged into an extension for ease of use and general good karma. Besides, it took about thirty seconds to hack up based on Back/Forward Dropdown Remover.