A few blogs around the net have posted lists of subjects most bloggers never talk about.
I found the use of silly voices while gaming to be the most interesting to me.
Usually when I DM a dragon or large creature i drop my voice to a more bass octive and slow my speech. Lithe sprites and pixies and simular get a fast and high voice. My dwarves to sound scottish. Flambouyant knights and sword swingers tend to the french ala Three Musketters.
Voices and accents have been a big part of my DMing style years.
Voices go hand in hand with posture and facial expressions. Dramatic npc's require dramatic gestures. When i want a villian to seem more menacing i stand and try to get into my players comfort zones. If i can make the players remember an NPC i did a good job.
I know voices arent for eveyone. I just happen to think they are indespencable to me.