John Stuart Mill- a utilitarian philospher who lived in England during the mid 1800's. Individualist whose two most compelling works are On Liberty and Utilitarianism.
John Locke- an individual rights philospopher born in England who is one of the premiere thinkers on the social contract. His Second Treatise of Government is considered one of his best works.
Thomas Hobbes- a philosopher during the 15th century that developed a philosophy concerning absolute national sovereignty. His Leviathan explains his view of the social contract, quite opposite of that of Locke's.
John Rawls - a twentieth century American philosopher that developed a notion of justice that is quite different than many others. Rawls proposes that in order to develop a just society an individual needs to be taken out of the society and then told to develop it as fair as possible. The individual is not aware of what part of society they will be put in, and so thus makes a very fair society. His work, Theory of Justice, further explains.
Jean-Jacque Rouseau- a French philosopher that developed the third idea of the social contract, in which decisions by the society need to be made by public approval or the common good. His work, The Social Contract, explains that no matter if the decision is bad or good, the sociery has to listen to what the citizens want.
Immanual Kant- a German philosopher who is considered by many to be the most brilliant philosopher of all time. Kant believed in the idea of universal morality, or the categorical imperative.
More to come...
Some cool Philosophy Links