For those of you planning on world building a custom world, creating a richer culture within an existing world, or trying to create a character with a cultural background rather than simply a personality, I can't recommend the Culture Shock series of books enough! At the risk of sounding like a salesman, these books really break down other cultures to give a sense of the different customs in particular locations from their preferred method of greeting to their thoughts on punctuality to whether they find it rude if you eat everything on the plate (indicating they didn't feed you enough) to if you leave food on the plate (indicating you didn't like the food).
Just for the record, I'm not paid by the Culture Book series or any other publisher (I wish) but have simply come across these books and found them utterly fantastic. Go down to your local library to borrow a few and see what you think. You can always purchase them if you like them or if your library doesn't have the particular countries you're looking for.
And no, as far as I know there are now Medieval or Victorian Culture Shock books (though that would be cool). However, a lot of these customs have been around awhile and are still worth reading up so that you can add those rich little details that make all the difference.