In a recent blog post by Mike Cohn, he wrote about Establishing a Common Baseline for Story Points. He explores the technique of getting estimators in a room from many teams. Perhaps a pair of individuals per team.
The entire room uses Planning Poker to estimate stories. The focus is on getting all of the folks in the same ballpark when it comes to estimating their stories level of effort.
The idea is not to have everyone become a clone of each other. But to get the story points close enough so that forecasting can be done across the teams. So, consistency without normalization or fixed rules.
Not only do I like this approach, but I’ve also successfully used it with several companies where I’ve coached. Not as an external coach, but as an internal coach. And it works quite well.