The American Civil Liberties Union (ACLU)
The ACLU is an organization working in U.S. courts, legislatures and communities to preserve the Constitution and laws of the United States. For example:
1954 - Brown v. Board of Education The ACLU, having joined the NAACP in the legal battle for equal education, celebrated a major victory when the Supreme Court declared that racially segregated schools were in violation of the Fourteenth Amendment.
2001 to Present - Rolling back un-Constitutional expansions in Government
The ACLU is working to restore fundamental freedoms lost as a result of post-9/11 expansions in the federal government's power to invade privacy, imprison people without due process, and punish dissent.
Other cases and causes (a small sampling):
1925 - The Scopes Trial
1942 - Fighting the Internment of Japanese Americans
1973 - Reproductive Rights in Roe v. Wade and Doe v. Bolton
Free speech and the free press
Equal treatment for lesbians and gay men
Exposing U.S. government-sponsored torture
Protecting the Right to Privacy
See also http://vimeo.com/9190177