A friend of mine was just alluding to Paul Fussell's book Class: A Guide Through the American Status Systems. I found a list of Fussell's categories, and they're interesting.
Top Out of Sight — Billionaires and multi-millionaires. The people so wealthy they can afford exclusive levels of privacy. We never hear about them because they don't want us to.
Upper Class — Millionaires, inherited wealth. Those who don't have to work. They refer to tuxes as “dinner jackets.”
Upper Middle — Wealthy surgeons and lawyers, etc. Professionals who couldn't be described as middle class. I suspect this is the class to which I, an engineer, am supposed to aspire.
Middle Class — The great American majority, sort of.
High Proletarian (or “prole”) — Skilled workers but manual labor. Electricians, plumbers, etc. Probably not familiar with the term “proletarian.”
Middle Prole — Unskilled manual labor. Waitresses, painters. (In other words, my mom and dad!)
Low Prole — Non-skilled of a lower level than mid prole. I suspect these people ask “Would you like fries with that, sir?” as a career.
Destitute — Working and non-working poor.
Bottom Out of Sight — Street people, the most destitute in society. “Out of sight” because they have no voice, influence or voter impact. (They don't vote.)
That's more slices than in Ruby K. Payne's terrific A Framework for Understanding Poverty, which is a chaotic but insightful book that does a a simple split into only upper, middle, and lower classes that is really illuminating about the cultural elements of class, especially around “common knowledge.” I like the way Fussell cuts that into more categories—the distinctions at the high and low ends of the scale are particularly clever, I think—but I don't like the way it's close to being a simple linear scale from high and low.
I'm not a real sociologist, but I think of class in the US in more categories, to reflect some cultural distinctions among folks who may overlap in wealth and income but do different kind of work and have different culture and distinct social networks. I've talked about this before, but not really laid out all of the categories I have in my head. So here they are:
High, middle, and low aristocracy
Inherited wealth. Low means rich enough not to have to work, medium means able to afford the trappings of wealth, high means hundreds of millions of dollars or more. As Fussel observes, these folks spend their wealth making themselves invisible, especially as you move further up the scale.
Major and minor celebrities
This includes not only obvious movie and pop stars but also big-name politicians, a few entrepeneurs like Bill Gates, atheletes, and so forth. Fame is a different kind of currency than wealth, and it comes with its own social circle and culture. “Major” celebrities can presume a permanent place in this class; “minor” celebrities cannot.
Entrepeneurs, CEOs, and so forth who have made enough money that they don't have to work ... but almost certainly continue to work, and work hard. These people may have wealth comparable to the middle aristocrats; at the point where they have as much money as high aristos they are better conceived as part of that artistocratic class, while at the low end they blur into the richest end of high professionals.
High and low professionals
People who make their living with some valuable mental skill. High professionals include successful doctors, lawyers, and corporate executives who make a lot of money ... but not enough that they can just quit working. Low professionals include just about everybody else who works in offices, from architects to customer service representatives, which means a broad range of actual income.
People who make their living with some valuable knowledge. Professors, scientists, and other experts of various kinds, including many artists. Often mistaken for professionals, but these folks have more (and stranger!) books in their houses. Again, covers a very broad range of actual incomes.
People who devote themselves to art or entertainment (though that last may simply mean entertaining themselves). Musicians, actors, bartenders, sex workers, nightclub bouncers, twenty-four hour party people. Keeping late or odd hours is a key defining characteristic.
High and low working class
People who make their living through physical work. The high working class have valuable skills, like plumbers or construction workers, while the low working class don't.
People working, often working hard, but perpetually worried about money because they're a paycheque away from economic disaster and homelessness, and don't have a route to improve that situation.
People unable to connect to the above-board economy. This ranges from the hungry homeless to folks currently hustling up wealth on a par with the upper end of the low working class ... but without any stability even at the day-to-day scale.
If this stuff interests you, I have an old post on the subject with a discussion of the relation between wealth and power and the distinction between professional and intellectual class.
Update: I should observe that practically all of the people ranging from the high professionals to the low working class refer to themselves as “middle class.”
Update: Realized I need to add bohemians to my personal taxonomy.