Pierre-Joseph Proudhon was, by most reckonings, the first great modern anarchist thinker, and the most influential, with the possible exception of his Russian disciple, Mikhail Bakunin. His writings and thought are still a major influence on the liberetarian socialist wing of anarchist thought. The French Revolution of 1848 claimed to take its inspiration from his thinking, though he was personally quite dissatisfied with the results and ideology of the Revolution.
Proudhon's thought was influenced heavilly by the French utopian Socialist Charles Fourier, and his own experience with working class revolutionary groups. In many ways, Proudhon's ideas for society resemble Jeffersonian federalism closer than anything else: all power devolved to the purely local level, with co-operation between the local groups only when it became neccessary. He felt that the dissolution of the centralized state, and its monopoly on currency and economic control, would allow workers to recieve a fair price for the products of their labor.
Proudhon and Marx knew each other, and came to quarrel extensively, in print, over the role of the state in Socialism. The rift between the liberetarian and authoritarian Socialists grew more and more irreconcilable, and finally came to a head at the meeting of the First International, after Proudhon's death, with Bakunin and the anarchists making a visible and public break from the Marxists.