So there's a few things you can start off with:
- Check out the new dungeon finder (and farm those Emblems)!
- Head into the new Icecrown 5-player dungeons
- Try and get the Quel'Delar
- Buy a new bag
- Start planning for the fishing tournament in Northrend
- Assault Icecrown Citadel itself
- Run a nerfed version of Oculus
- Send your Heirlooms to your toons of the opposite faction (on the same account).