Other
Australian National University: Introductions to Marxism
A useful collection of links to "Classical Marxism" texts. Most of the links lead to substantial readings from primary sources.
Marxists Internet Archive
Marxists Internet Archive: Communism
Taken directly from the writing of Marx, Engels and Lenin, this entry from the Marxists Internet Archive also includes explanation of the quotations. Very detailed, it will require some sophistication on the part of the reader. Gives an...
Marxists Internet Archive
Encyclopedia of Marxism: Homepage
This site from the Marxists Internet Archive provides a detailed explanation including quotations from Engels and Marx, as well as explication. Links defining terms are helpful, as is the suggested further reading link.