On Architecture - Text of the English-language translation of 1826 by Joseph Gwilt, as well as a French translation and the Latin text (Teubner 1899 edition), hosted by Bill Thayer in his Lacus Curtius site. - http://penelope.uchicago.edu/Thayer/E/Roman/Texts/Vitruvius/
Vitruvius Pollio, The Ten Books on Architecture - The full text of the English translation by Morris Hicky Morgan (1914), hosted by the Perseus Project. Easy navigation through the text; map of sites mentioned. - http://www.perseus.tufts.edu/cgi-bin/ptext?doc=Perseus:text:1999.02.0073
Plates from Cesariano's Edition of Vitruvius - Woodblock illustrations were added to Vitruvius's text in the edition published by Cesare Cesariano (Como 1521). Images from Art Serve at the Australian National University. - http://rubens.anu.edu.au/htdocs/bytype/arch.sources/vitruvius/
Vitruvius, On Architecture - 12 plates from an 18th-century Venetian edition, hosted by the University of Pennsylvania. - http://ccat.sas.upenn.edu/george/vitruvius.html