Here is a small patch, done against svn rev 24060, that adds "Show All Layers" to the View3d -> View menu. This is one of the items in the the 2.5 Beta 0 todo list.
I have included a screen shot showing the new menu item in the "View" menu.
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I've added more to the view menu so the patch has been updated. The one to use now is space_view3d_diff.txt.
I added "Center Cursor and View All" and "Align Active Camera to View" to the align view submenu. align_view.jpg shows what the menu now looks like.