The General is, depending on the time of day, the largest corporation in the world or number two, generally tied with General Electric
In addition to the well known brands of American cars listed by Jizz, GM's international operations are responsible for Opel, Holden, Vauxhall, Hummer, and Saab, and own significant shares of Subaru, Fiat, Isuzu, and Suzuki.
In addition, GM Electro-motive is one of America's principal manufacturers of diesel-electric locomotives. They also produce engines for a variety of marine OEMs, such as Mercruiser, under their Vortec brand name. GM manufactures engines for a variety of other commercial brands, as well, and even for some consumer vehicles such as the new Honda pickup.
Their advanced R&D spinoff, Delphi, holds patents for a variety of technologies such as electronic four wheel steering and automotive night vision which are or will be used in many other vehicles. Also in GM's stable are XM satellite radio and DirecTV, product of the Hughes Electronics Corporation.
GM's bank, GMAC, is a complete full service bank with mortgage, investment, insurance, and consumer lending and credit card services. GMAC will also gladly serve as your realtor.
All this adds up to one of the greatest empires in history.