Visit the following links to find a wealth of sources and information on Marxism-Leninism:
Marxism-Leninism Study Guide, a topical catalogue of sources on various concepts.
Marxists Internet Archive, a collection of works from Marxists of all trends, from Mao Zedong and Josef Stalin to Leon Trotsky and Kwame Nkrumah.
Marx to Mao, a collection of works like the Marxists Internet Archive but with a more narrow focus on those writing in the Marxist-Leninist tradition.
Revolutionary Spirit, a theoretical journal and collection of works by the American Party of Labor, a Hoxhaist* party.
The Red Phoenix, a blog also by the American Party of Labor that contains various links to pieces of basic theory on the right-hand column, many of them relevant to current issues faced by Marxist-Leninists in the West.
*Hoxhaism is an ultra-orthodox interpretation of Marxism-Leninism in the tradition of the Albanian leader Enver Hoxha. The YCL generally does not follow as hard a line as do most Hoxhaists. The YCL maintains no formal affiliation with the American Party of Labor and does not identify itself as Hoxhaist, although members may and do.