Sadly, very little of Proudhon’s voluminous writings has been translated into English. Benjamin Tucker translated the First and Second Memoirs of What is Property? and volume 1 of System of Economic Contradictions and both are available on-line. He also translated numerous other shorter pieces. The First Memoir of What is Property? in a new translation is also available from Cambridge University Press. General Idea of the Revolution in the Nineteenth Century was translated in 1923 by John Beverley Robinson (available on-line). The First Part and chapter one of the Second Part of Du Principe Fédératif was translated by Richard Vernon under the title The Principle of Federation. Other selections (mostly related to his Bank of Exchange, extracts from his exchange with Bastiat and a few parts of volume 2 of System of Economic Contradictions) have appeared in Clarence L. Swartz’s Proudhon’s Solution to the Social Question. Selected Writings of Pierre-Joseph Proudhon edited by Stewart Edwards has a comprehensive selection of short extracts on various subjects.
Most anthologies of anarchism have selections from Proudhon’s works. George Woodcock’s The Anarchist Reader has a few short extracts, while Daniel Guérin’s essential No Gods, No Masters: An Anthology of Anarchism has a comprehensive section on Proudhon. Robert Graham’s excellent anthology Anarchism: A Documentary History of Libertarian Ideas, Volume 1: From Anarchy to Anarchism (300CE-1939) has selections from Proudhon’s major works.
The best introduction to Proudhon’s ideas is K. Steven Vincent’s Pierre-Joseph Proudhon and the Rise of French Republican Socialism, which places his ideas within the context of the wider working class and socialist movements. George Woodcock’s Pierre-Joseph Proudhon: A Biography is the best available and is essential reading. Other studies include Robert L. Hoffman’s Revolutionary Justice: The Social and Political Theory of P-J Proudhon, Alan Ritter’s The Political Thought of Pierre-Joseph Proudhon and Pierre-Joseph Proudhon: His Revolution Life, Mind and Works by Edward Hyman. J. Hampden Jackson’s Marx, Proudhon and European socialism is a good short overview of the Proudhon’s life, ideas and influence. Henri de Lubac’s The Un-Marxian Socialist: A Study of Proudhon is more concerned about Proudhon’s relationship with Christianity. Political Economy From Below: Economic Thought in Communitarian Anarchism, 1840-1914 by Rob Knowles presents a useful extended discussion of Proudhon’s economic ideas.
Shorter accounts of Proudhon and his ideas include Robert Graham’s excellent introduction to the 1989 Pluto Press edition of General Idea. Jack Hayward has a comprehensive chapter entitled “Proudhon and Libertarian Socialism” in his After the French Revolution: Six Critics of Democracy and Nationalism. Martin Buber’s Paths in Utopia contains a useful account of Proudhon’s ideas. Other useful short pieces on Proudhon include George Woodcock’s “Pierre-Joseph Proudhon; An Appreciation” (in the anthology Anarchism and Anarchists) and “On Proudhon’s ‘What is Property?’” (The Raven 31). Daniel Guérin’s “From Proudhon to Bakunin” (The Radical Papers, Dimitrios I. Roussopoulos (ed.)) is a good introduction to the links between the French Anarchist and revolutionary anarchism. Charles A. Dana’s Proudhon and his “Bank of the People” is a contemporary (1849) account of his economic ideas.
George Woodcock’s Anarchism: A History of Libertarian Ideas and Movements and Peter Marshall’s Demanding the Impossible: A History of Anarchism, both have chapters on Proudhon’s life and ideas. Daniel Guérin’s Anarchism: From Theory to Practice is an excellent short introduction to anarchism which places Proudhon, with Bakunin, at its centre. Max Nettlau’s A Short History of Anarchism should also be consulted.
For those Marxists keen to read a generally accurate and sympathetic account of Proudhon, albeit one still rooted in Marxist dogmas and dubious assumptions, then John Ehrenberg’s Proudhon and His Age would be of interest.
 It is only marred by Vincent considering anarchism as being incompatible with social organisation and, as such, Proudhon’s theory “conflicts with the traditional concept of anarchism” and so he was not an anarchist in the “popular meaning”! (269, 234)
 For a short critique of Ehrenberg’s Marxist assumptions, see K. Steven Vincent’s review (The American Historical Review 102: 4 ).