Another of our members sent in this interesting tidbit:
Todmorden Mills, which has been through several incarnations (mill, riding stables, and now historical site), houses a theatre for which I volunteered. While I never experienced anything unusual, several people who work there swear that it's haunted. There are two stories that I know of.
The first is of an old woman, who seems quite harmless and friendly. She's been seen by a couple of people, walking about the theatre late at night.
The other is less pleasant, but certainly not threatening. Loud noises like moving furniture or props can be heard from the loft spaces late at night when no one is around, and people working in the sound booth above the audience have seen a grey form flash past the windows overlooking the stage (the windows are about 20' above the ground).