What a fun site this is: www.arthurlloyd.co.uk/LondonsLostTheatres
Great pics of London's old theatres, combined with photos of what they look like now. I like the stories about Lily Langtry and Sarah Bernhardt being on stage in various places like Clapham.
There's so much stuff here, you could waste a long, wet afternoon looking at it all. What a fun resource.