3 links
Ancient Greek Skepticism
iep.utm.edu
An article on skepticism in Ancient Greece from the Internet Encyclopedia of Philosophy, by Harald Thorsrud of Temple University.
Ancient Skepticism
plato.stanford.edu
From the Stanford Encyclopedia of Philosophy, by Leo Groarke. Article on the two movements in ancient philosophy, Pyrrhonism, and Academic Skepticism.
Aporetic Philosophia
aporeticworld.com
A discussion of the development of Greek skepticism from Pyrrho to Sextus Empiricus. A reference provided by Aporetic World Music.