Barlaam and Ioasaph - The story of Barlaam and Ioasaph, by "John the Monk". Traditionally ascribed to St. John Damascene, but possibly actually the work of St. Euthymius the Georgian.
Barlaam and Ioasaph - Each chapter in its own file, with links to previous, next, table of contents, or any other chapter. If you are using a graphical browser, this is the online equivalent of a "large print" edition.
An Exact Exposition of the Orthodox Faith - Appears to be the same translation as at CCEL, but without notes. The benefit of this version, at St. Nicholas Orthodox Church, Dallas, is that you can jump to a particular chapter.
An Exact Exposition of the Orthodox Faith - Each of the four books in its own HTML file, with notes, at Christian Classics Ethereal Library. From A Select Library of Nicene and Post-Nicene Fathers of the Christian Church, second series, vol. 9.
In Defense of Icons - Two excerpts from the writings of St. John of Damascus.