John Stuart Mill (1806 - 73) formed the Utilitarian Society which met to read and discuss essays. His works include On LIberty and Principles of Political Economy.
Jeremy Bentham (1748 - 1832) set out to theorize a simple and equitable legal system. The law of utility, for which is best remembered, states that the goodness of a law can be measured in accordance with the measure in which it subserves the happiness of hte individual.
Alan Ryan is Warden of New College, Oxford and is currently on sabbatical in Stanford. His other books include Property and Political Theory and Bertrand Russell: A Political Life.