Who lives in Meredith's house: 

I've had to edit this several times over the past few days, and different individuals keep changing it back.  In assuming good faith, I will guess that these are individuals who have not yet been able to watch the full third season.  However, as of episode 3x18, "Scars and Souvenirs", which has aired in the United States and Canada, Alex Karev is a resident of Meredith Grey's home.  George had moved out prior to episode 3x15 "Walk on Water", leaving his room vacant as he moved into the Archfield Hotel with his new wife, Callie Torres.  Alex moved in and took residence of the room that George once lived in.  The rent paying housemates are Alex and Izzie, not Izzie and George.