It's not technically an attunement, but there is a series of quests that guide you through the introductory 5 Player Dungeons surrounding Icecrown Citadel. You don't have to do these dungeons to get into the normal versions of Icecrown, but it sure brings a lot to the experience. I guess, in a sense, you can think of it as a simplified attunement.
Additionally, the gear that drops from these first three instances will go a long way towards catching up people to the ICC raid. In my raid, we call this "bootstrapping." There's a bunch of reasons you might need to bootstrap folks: a tank rotation, new people, meteor crashing into the planet, what have you.
As you do the quest, you'll enter (and do battle in):
So, let's take a look at these three instances and how to blur through them.