I can see that the previous posts focused on post-war American films with male leading characters. You might want to look at films from other national cinemas and different eras such as:

-Strike (1925) and Battleship Potemkin (1925) by S. Eisenstein: they contrast individualism and collectivism. In particular, Strike portrays the oppresive forces of economic materialism through visual metaphors (animal slaughter, lemon squeezers) that are interwoven in the narrative through an editing completely different from Hollywood.

-the Italian neorealist films Yesterday, Today and Tomorrow (1963), Marriage, Italian style (1964) both directed by De Sica and starring Sophia Loren and Marcello Mastroianni. The former is an anthology of three episodes where the themes of love (and sex), gender and materialism are closely connected. The episodes contrast the materialism of the upper classes with the ways the disinherited are forced to adopt to survive. episode one (Adelina) shows the connection between motherhood and materialism as Adelina is forced to give birth to babies to avoid jail. In episode two, snobbish Anna remains indifferent when she almost runs over a child while on her husband's Rolls Royce with her lover. In episode three, the prostitute Mara has to cope with the materialistic demands of her clients and her spirituality. Marriage, Italian Style links the sacred institution of marriage to materialism and economic stability. Filomena who has been the mistress of a rich businessman for decades decides it is high time he married her and supported the entire family;

-on the relationship between sex, gender and materialism also check the Visconti episode in Boccaccio 70, where Romy Schneider decides to become a prostitute;

- Bycicle Thieves (1948) again by De Sica, following a man's desperate search for his stolen bike through the streets of Rome. The bike is essential for his job. It could be interesting to see how The Icicle Thieves (1989, Ladri di saponette) pays homage to De Sica's film by showing how the corrupting power of advertising and materialism brings the characters of De Sica's film in a consumerist heaven (or hell?).

- Human Resources by L. Cantet (1999) showing how an idealist trainee manager has to come to terms with the materialism of economic production;

- Los Lunes al Sol by Ferndando De Aranoa (2002) following the crises of middle-aged Spanish unemployed;

- Rosalie Goes Shopping by Percy Adlon starring Marianne Sagebrecht of Bagdad Café as a German bride who learns to use credit cards without having any money;

- Le couperet (The Ax, 2005) by Costa Gavras: a dark satire of downsizing and outsourcing where a fired executive becomes a serial killer. Why not looking at this together with American Psycho?

The previous posts did an excellent job in identifying films that possess a theme of materialism present.  I think that I can find others that have the same theme evident.  While it's not a driving force, "North Dallas Forty" is a film that shows how materialism is a corrupting force in the world of sport, specifically football.  In a domain where athletes are treated as commodities, as opposed to individuals, materialism is a driving force in the decisions of the football theme.  Materialism is a subtext of "The Matrix," in that individuals who are plugged into the system are subdued with content pleasures of material objects and do not examine what lies beneath the surface in a world of social control.  "Glengarry Glen Ross" is another film where materialism is vitally important in that each salesman is measured in value of how much money was made and how much profit was turned.

One of the other posts mentioned Wall Steet with Michael Douglas. That's the first one that came to mind. Other examples:

• THE FIRM.  This is the Tom Cruise movie based on the novel by John Grisham. A firm of lawyers are willing to look the other way toward the murder of several of their own cohorts when it comes to covering up their involvement in illegal overbillings and mob connections.
• BOILER ROOM.  This one deals with a group of young stock brokers at an unscrupulous firm who push "pump and dump" stocks from defunct companies that artificially create high demand. When the stocks (many of them worth a penny) rise to $3, the firm collects, but the investors lose everything. Starring Giovanni Ribisi, Vin Diesel, Ben Affleck.

Three movies that have the theme of materialism:

1. Citizen Kane (1941)  This classic film is a one that students of cinematography study.  Produced by Orson Welles in retaliation for a snub from newspaper magnate William Randolph Hearst, this movie chronicles the rise to power of the publishing giant, his quirks, and his odd affair with Susan Alexandra.  One of the first films that demonstrates that the American Dream is not all it is cut out to be, it also introduced new aspects of making films.
2. Wall Street (1987).  Michael Douglas plays Bud Fox, a Wall Street stockbroker who wants to climb the corporate ladder.  When he ingratiates himself to Gordon Gekko, Fox believes he is on his way, but his revelation to Gekko about transactions involving his father's airline company prove disastrous to the family as the unconscionable Gekko engages in insider trading based on Fox's tip.
3. The Fight Club (1999)  An unnamed protagonist played by Edward Norton is an "Everyman" who is discontented with his white-collar job.  He forms a fight club with soap saleman Tyler Durden and becomes embroiled in relationships with Durden and a dissolute woman in his struggles to become rich.

"Scrooged" based loosely on A Christmas Carol by Dickens, this shows a TV producer living an incredibly lavish lifestyle but being incredibly corrupt at the same time.  Really fun.  Obviously you could also go back to any movie of A Christmas Carol for the same themes.

Another is "Family Man" with Nicolas Cage where he plays an incredibly wealthy hot shot who gets the chance to go back and see what his life might have been like if he had chosen differently.  With a family he realizes what was important and it wasn't all his money.

Another one is Nicolas Cage's "It Could Happen to You," in which his wife is the greedy one and she plays a nasty greedy person and by contrast we see his character being happier and nicer and better because he is willing to give away half his money.

There is a somewhat inverted view of materialism in The Blindside, where we see a poor kid taken in by a well-to-do family that draws no distinctions via class or race in their treatment of him.

The film is a bit glossy, naturally, but the film does do a surprisingly good job of ignoring exactly the same issues it addresses - which in this case is a positive achievement, overlooking that which really should be overlooked and, in doing so, making a statement about what is worth paying attention too (regarding class, social position, race, etc.).

There are many movies that depict materialism.  The ones that first come to mind are The Great Gatsby The Devil's Advocate and Wall Street.   Wall Street has already been mentioned, but I think The Devil's Advocate is a perfect depiction of the problems with materialism.

2006 The Devil Wears Prada - The cutthroat business of high fashion is explored in this film.

1989 War of the Roses - A married couple try to get each other to leave the house in a vicious divorce

1987 Wall Street -A young and impatient stockbroker will do anything to get to the top.

1975 Network - Executives at a major network are only concerned about ratings; they exploit a news anchorman who has lost his mind and project him as a modern-day prophet for their profit.