Shortcut key for bookmark toolbar in Firefox

Alt + V, T, B

Open "View" menu > Toolbars > Bookmarks Toolbar

You can use Hide BookmarksBar extension

You can use the Keyconfig add-on and this script:

var toolbar = document.getElementById("PersonalToolbar");
toolbar.collapsed = !toolbar.collapsed;
document.persist(toolbar.id, "collapsed");

After installing Keyconfig, press Ctrl + Shift + F12 to bring up the key binding interface. Create a new shortcut using the code above, and bind it to any key combination you want. Tested and working in Firefox 3.5.5.