Xmarks is the #1 bookmarking and open tab add-on. Keep your bookmarks, and open tabs backed up and synchronized across computers and browsers. Mobile phones with Premium access. Utilize LastPass to sync passwords!
Session Manager saves and restores the state of all or some windows - either when you want it or automatically at startup and after crashes. It can also automatically save the state of open windows individually.
Visual bookmarks for Firefox. (Works with all latest versions of Firefox)
A productive way to organize, read and share the content of your favorite feeds, blogs and news sites. Feedly offers a seamless transition from Google Reader.
This provides separated "Bookmarks" Sidebar panel like Opera.
Tired of that boring default icon next to your bookmarks? This extension adds an interface allowing you to pick the icon for each of your bookmarks.
Detects Duplicate Bookmarks when bookmarks are added and specify where is the previous URL. You can also search and delete duplicates URL already in your Bookmarks.
Firefox 13 support is available from http://bookmarkdd.mozdev.org in version 1.1.1.
Use context menu or Bookmarks menu to set mark lines within long pages. Navigate to marked pages and to the marked lines.
Highlight interesting sections of text, navigate between highlighted sections.
Bookmark Previews adds an album view and thumbnail view to the bookmarks manager.