Work defines a large portion of life in any society, traditional or modern. How should we think about the social and economic forces that create "work"? What are the institutions and practices through which individuals use their bodies, brains, skills, and talents to create value within a given set of economic relationships? These questions are just as relevant in consideration of the medieval economy -- serfs and freemen, artisans, highwaymen, retainers, soldiers, the odd banker -- as they are for the contemporary economy. (It would be very interesting to analyze Marc Bloch's account of feudalism from the point of view of the kinds of skilled work he identifies in the medieval manorial economy in Feudal Society: Vol 2: Social Classes and Political Organisation.)
So what does the division of labor look like in the contemporary economy? And how is it changing?
The Bureau of Labor Statistics maintains a "Standard Occupational Classification System" encompassing tens of thousands of job types, organized into 23 major groups (link). (My own profession, philosophy professor, falls in category 25-1120 "Arts, Communications, and Humanities Teachers, Postsecondary".) Here is the table of major groups of occupations:
The International Labour Organisation maintains a different classification system of occupations (link). This system includes managers, professions, technicians and associate professionals, clerical support workers, service and sales workers, skilled agricultural, forestry, and fishery workers, craft and related trades workers, plant and machine operators and assemblers, elementary occupations, and military workers.
It is interesting and important to observe the trends of change that can be observed in the distribution of tasks across categories of worker over time -- the evolution of the division of labor in society. A good beginning would be a table indicating the percentage of the labor force in each category. It would be very interesting to see the shifting distribution across these categories over the past 75 years -- though I can't easily locate a study that provides this kind of analysis. Presumably a century-long comparison would demonstrate a major shift in the BLS groups from group 45 (agriculture) to groups 47, 49, and 51, and a later shift to service occupations like groups 31, 35, 37, 41, and 43 in the past thirty years. (The BLS SOC is revised periodically, most recently in 2010, so comparison across time is presumably non-trivial.)
It is evident that there is a generally falling scale of authority, compensation, skill, and prestige across both sets of categories. So the division of labor, as expressed in these classification systems, proceeds from low-skill, low-specialization at the bottom, to high-skill, high-specialization at the top.
So the question of skill and division of labor is not exclusively one of sociological theory; it is a statistical feature of the social order that is amenable to direct empirical research. But the arrangement of the occupations in a society is not solely a question of economic efficiency. It is also directly tied up with the distribution of power and authority in society. Assigning a person the title of "manager" or "director" not only reflects the individual's skills; it also assigns him or her a measure of power and authority.
(It is mildly interesting to note that there is a whole slice of specialized work in contemporary society that is not included in either classification: extra-legal activities like smuggling, piracy, gambling, organized crime, drug dealing, etc. These activities also have their own specialized division of labor, ranking of skills, and rates of return.)