Two more US realms have opened today, adding to the two new realms last week. Both realms are in the EST timezone and include Undermine, a PvE realm in Battlegroup 10, and Anub'arak, a PvP realm in Battlegroup 11.
Both of these realms will be closed to paid character transfer for six months, as opposed to the previous three months. (And if you're playing on a realm not yet open for transfers, the new six month limit applies to you as well.) So if you were looking for fresh adventures in Azeroth, this is a great chance.