With Firefox you can bookmark to either the dropdown menu or the toolbar, or both. You can also create a new bookmark folder on the toolbar and add multiple bookmarks to it.
I saved my commonest bookmarks - my three different hotmail addresses and PPRuNe - to a folder on the toolbar. When you place your mouse pointer on this folder, a drop down menu shows all four bookmarks and an 'open in tabs' choice. If you click on this choice, it automatically launches all four bookmarked sites in one go, each in their own tab. Its a bit like having multiple windows open but much simpler to operate. Beware of having too many bookmarks in one folder though - four at one time is about the maximum for smooth operation.