Diodorus Siculus: Βιβλιοθήκη ἱστορική – Historical Library
Diodorus' text has only partially survived: we have Books I–V and XI–XX intact, while the remaining books (VI–X and XXI–XL) survive only in fragments. The 12-volume Loeb translation by Oldfather et al is partly available in HTML versions from Theoi.org (vols. 2, 3) and Perseus (vols 4–8); Booth's full two-volume translation of 1814 is available as scanned books from the Internet Archive.

Diodorus Siculus, trans. Oldfather, Sherman et al (1933–1967) Library of History (12 vols). London; Cambridge, Mass: Heinemann; Harvard University Press. http://www.theoi.com/Text/DiodorusSiculus4A.html (Books IV–VI)

 
Diodorus Siculus, trans. Oldfather, Sherman et al (1933–1967) Library of History (12 vols). London; Cambridge, Mass: Heinemann; Harvard University Press. http://www.perseus.tufts.edu/hopper/text?doc=Perseus%3atext%3a1999.01.0084 (Books IX–XVII). 

Diodorus Siculus, trans. Booth (1814) The Historical Library of Diodorus the Sicilian (2 vols). London: Printed by W. McDowell for J. Davis. —In fifteen books, to which are added the fragments of Diodorus and those published by H. Valesius, I. Rhodomannus, and F. Ursinus. http://archive.org/details/historicallibra01bootgoog [Vol 1, Bk I–V; XI–XIV] http://archive.org/details/historicallibra00bootgoog [Vol 2, Bk XV–XX, fragments].