Answer by Peter Leykam:
Sociology and cultural/social anthropology initially split their focus between Western industrialized societies and non-Western, non-industrialized respectively. While this distinction no longer holds true – you find anthropologists studying Wall Street investment bankers, and sociologists studying rural peasants – this early division of labour influenced the development of the two fields. Anthropologists tend to be more qualitative and seldom make extensive (or any) use of quantitative analysis. Sociologists tend to be more quantitative in their analysis. Anthropologists tend to view themselves as questioning how cultural categories are created, whereas they view sociologists as taking cultural categories for granted (I'm sure sociologists have their own ideas of those differences). And sociology tends to be more focused on public policy than anthropologists. However, there is a lot of overlap between the two fields – with sociologists doing excellent urban ethnographies – and with people in both fields drawing on many of the same sources – Durkheim, Bourdieu, Foucault, etc.
These days Social Anthropology and Cultural Anthropology are generally interchangeable. Back in the earlier days of Anthropology there was a split between British anthropology, which focused on social structure, and American anthropology, which focused on systems of meaning. Culture is the shared system of meanings that people live in and through, "Webs of signification that we weave ourselves." Social structures are durable sets of social relationships that exist separate from any individual that occupies a given set in the structure. So you will move from being a son to a father and grandfather, but a family structure exists independent of your movement through those roles.
Today it is generally taken for granted that cultural systems exist within social structures, and that social structures are created and reproduced through cultural values. So, while individual authors might emphasize one aspect or the other, they are generally seen as mutually constitutive.