Landgraab Industries is a large business corporation owned by the Landgraab family. If it is not the largest corporation in SimNation, it is likely one of the largest.
It is mentioned in some of the business chance cards. When a Sim first gets a job in the business career, they most likely work for Landgraab Industries. In The Sims 3, the science lab in Sunset Valley is the Landgraab Industries Science Facility. Landgraab Industries also owns Shiny Things Inc., the company that made the buyable Servo in The Sims: Livin' Large, also many kitchen appliances in the game are made by Shiny Things Inc.As mentioned in a a chance card of the bussiness career track, Landgraab Industries wanted to buy Wrightway Toys, a toy making company.
Big Yard Dudes Inc might be a sub-division of Landgraab industries but it is very unlikely.