"Organize Bookmarks" has been renamed to "Show All Bookmarks" in the bookmarks menu. Though there are some differences, it offers similar functionality.

I am aware of the different name.........It's the interface I don't care for. Is there any way to change it back to the old interface? This one difference has kept me from upgrading my browser since FF2, which is no longer supported.

No, you can't use the old interface in Firefox 3.0+ versions, including Firefox 4.0. Firefox 2 and earlier versions used a completely different storage system (bookmarks.html) for bookmarks than the later versions use (places.sqlite).

See if either of these articles help you get beyond your dislike of the new system.
http://kb.mozillazine.org/Sorting_and_rearranging_bookmarks_-_Firefox
http://kb.mozillazine.org/Sorting_bookmarks_alphabetically

Thank you so much! At least now I can quit looking and work on getting use to the new version, or look for a different browser.

WHY DID YOU TAKE AWAY A REALLY GOOD THING AND TURN IT INTO CRAP??

WHY?

LEAVE THINGS ALONE!!' YOU MADE IT WORSE. WHY?????

The Firefox 2.0 bookmarks interface has been gone for like three years now, kinda slow with your complaint, aren't you?