Staff Wars - excellent free note-naming games with a space theme. Great for middle school and works really well on an interactive whiteboard. One of the many games from The Music Interactive Gotta do this at DC!
Spell-a-staff Grand Staff Game for Practicing Note Names
Drill viola clef note names with this printable memory/concentration game. Select cards (note cards and alphabet letter cards). Then test your memory and your ability identify the notes of the viola clef.