Thank you to our December/Janurary Prefect, Preciousrosebud for this information!
Our Founder: Rowena Ravenclaw
Ravenclaw Common Room
Ravenclaw Tower is located on the west side of Hogwarts, on the fifth floor, and is the location of the Ravenclaw common room and dormitories. The entrance to the room is at the top of a spiral staircase, and is a door without doorknob or keyhole but a bronze knocker in the shape of an eagle. In order to enter the room, you must answer a question asked by the eagle knocker; if you answer wrong, you must wait for someone who gets it right.
The Ravenclaw common room is one of the more airy rooms at Hogwarts. It is a wide, circular room with a midnight blue carpet, arched windows hung with blue and bronze silks, and a domed ceiling painted with stars. During the day, the Ravenclaw students have an excellent view of the surrounding mountains. The room is furnished with tables, chairs, and bookcases; and by the door leading up to the dormitories, there is a tall statue of Rowena Ravenclaw made of white marble. It is the highest tower excluding the Astronomy Tower.
Scarf & Tie
In the books the Ravenclaw Colors are Blue and Bronze, though, it in movies, it's Blue and Silver as presented in the tie and scarf.
Our Mascot is the Golden Eagle, not the Raven.
The Dark Lady - Helena Ravenclaw, Rowena's daughter is our House Ghost.
Ravenclaw Diadem - the wearing of this diadem increased your intelligence.
The story of Helena Ravenclaw and the Diadem is tragic, It's the reason why is is a ghost.
Helena Ravenclaw was killed by the Bloody Baron. She informs Harry that she stole the Diadem of Ravenclaw from her mother, in an attempt to become smarter than she, and then went into hiding in Albania. It was a dying Rowena Ravenclaw's wish to see her daughter again and so sent for the Bloody Baron to look for her, knowing that he would not rest until he brought her back. However, she refused to come with him and in a moment of blind rage, he killed her with a single stab wound to her chest. Overcome with remorse, the Bloody Baron killed himself using the same weapon in turn. The diadem remained in the hollow of the tree in the Albanian forest until Tom Riddle managed to charm the story out of her ghost, The Grey Lady. Riddle, who had been seeking out historically significant objects to make into Horcruxes, later retrieved the diadem from Albania and hid it in the Room of Requirement at Hogwarts while visiting the castle years later.
As far as The Bloody Baron - he is the Slytherin House ghost. He is the only person besides Dumbledore and Fred and George Weasley who can exert any control over the Poltergeist Peeves; Peeves is terrified of him for some unknown reason, referring to him as "Your Bloodiness" and "Mr Baron."
The Baron's nickname comes from the fact that he is covered with blood, which appears silvery on his ghostly form. When Nearly-Headless Nick is asked in the first book why the Baron is so bloody, Nick delicately comments that "[he has] never asked". However, this is explained in Harry Potter and the Deathly Hallows, when Helena Ravenclaw tells Harry that the Baron had been in love with her when the two were alive, and when she ran off with the diadem, Rowena Ravenclaw sent the Baron after her, knowing he would not stop until Helena was found. When she refused to return with him, however, the Baron killed her in a fit of rage, and then, in remorse, killed himself with the same weapon. He has thus haunted Hogwarts ever since, wearing his ghostly chains as a form of penitence.