Biography.com: Xenocrates: Concise paragraph on his teachings.
Columbia Encyclopedia: Xenocrates: Concise paragraph on this early scholarch.
FOLDOC: Xenocrates: Entry from the philosophical database, with links to related entries.
Life of Xenocrates: Section from the Lives of the Philosophers, as compiled by Diogenes Laertius and translated by C.D. Yonge.
MacTutor History of Mathematics: Xenocrates of Chalcedon: Biography, bibliography and list of related topics.
Wikipedia: Xenocrates: Entry drawn from the 1911 Britannica.
Xenocrates: A detailed article by Russell Dancy on this thinker's life and teachings. From the Stanford Encyclopedia of Philosophy.