If you set Safari's Home Page address (Safari: Preferences, General tab) to bookmarks://, you can display the Bookmark Manager by clicking the Home button in Safari's main toolbar.
I use this trick to get a clickable icon for the bookmark screen without sacrificing the additional (albeit small) real estate consumed by the Bookmarks Bar.
Mac OS X Hints
http://hints.macworld.com/article.php?story=20051024192631707