On the ERWA writer's list, people have been sharing some great writer's resources. Google Images, YouTube, Flicker... Even writers know what a single picture is worth. Diaries are great. I've heard that there's an annotated copy of Pride and Prejudice that explains in great detail things like the carriages and the dresses, which is an incredible resource if you write historical fiction. (Love to read them, would die if I tried to write one.) Newspaper archives are tricky, because while we like to think that newspaper exist to present an unbiased account, that's a myth newspapers perpetuate but have never delivered on. But it's sort of fun to see how the writers hyped the stories. They're like ad copy writers with a longer word limit. Other writers are a great resource too.
Where do you turn for information?