Does your bookmark list resemble the size of the catalog of the Library of Congress? If you would find alphabetizing helpful, here's how to do it in Firefox:

Open the "Organize Bookmarks" window. In the left sidebar, select the group of bookmarks to be sorted. (Toolbar, Menu, etc.). Control-click for a contextual menu; then select "Sort by Name."

To alphabetize within bookmark folders, the same process must be done one-by-one.
Odds & ends of bookmarks that are loose "singles" will appear at the bottom of the list of alphabetized folders.

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P.S. - Couldn't find a method in Safari 3.2.1. Maybe there's a way in more recent versions.