The Man in the Iron Mask - Plain text. Also available for download as a zipped text file or zipped HTML file. At Project Gutenberg. - http://www.gutenberg.org/etext/2759
The Literature Network: The Man in the Iron Mask - Chapter indexed HTML of the complete text. Includes a search feature and author information. - http://www.online-literature.com/dumas/man_in_the_iron_mask/