I haven't had much time to write or edit, but I've thought a lot about it. Dave Wolverton (aka Dave Farland) had an excellent Daily Kick (an email everyone should sign up for--it has some great ideas) about how world building affects your character.
To sum up his email, these are the main questions to think about:
1. What kinds of social conflicts are likely to affect my characters?
2. What kind of education does my character have? (even farmers are educated about what they do)
3. What historical incidents might your character witness, or celebrate as the basis of holidays?
4. What types of entertainment will your character engage in?
5. What cultures might your character mingle with? Does he speak more than one language, or could he be a part of a couple of cultures?
6. What interesting sights or features in my world will affect my character?
As soon as I read some of these questions, I thought of a dozen things I could do to add depth and dimention to a few of my manuscripts. Each of these things will impact your characters in some way, and will help your world rise up off of the flat page and come to life.