I use small 'Mini' Poker Chips.
http://www.greathallgames.com/index_achipsDrops.html
They are 3/4" round and stackable. I use white for 1 wound, blue for 5 wounds, and red for activated markers. Yes, I only have red white and blue for now. I plan on ordering more soon. You can get these in multiple colors. I think they will make great markers for effects.