Although the United States Supreme Court has decided cases encompassing corporation law, the vast majority of precedent in this area comes from the state courts. These state court decisions are usually based on the statutes of that particular state. There is an entire digest topic devoted to "Corporations" in the West key numbering system. A researcher can either browse its topic analysis or use the Descriptive Word Index to find corporation cases using the applicable West digest.
Cases can also be found using online research. Both Lexis and Westlaw have databases devoted specifically to corporation law. These databases can be further limited to specific states, if that is desireable.
Finally, because most corporation cases involve interpreting a state's corporation act, cases can often be located in that state's annotated code.
Caveat: Even though most precedent on corporation law comes from the state, authority over certain ancillary issues may be federal. For example, securities law (regulating the registration and trading of stocks) is predominantly a federal issue.