Just outside each Common Room door

[glacial_queen]

Clustered at eye-level (assuming one was about 5'5 anyway) next to each common room door was a small flotilla of floating globes of witchlight, each about the size of a baseball. They were mostly white and yellow globes because they gave off the brightest light, though some light greens and blues and purples were interspersed just because they were pretty. The individual globes weren't terribly bright on their own, about comparable to a medium size flashlight.

They floated around a sign, which said: Free for the taking. Just grab one and it will follow you around all day! (Be warned, they'll probably fade by dawn.

--The Magic Reserves