Here you will find links to some key ancient and traditional source material on patience that's available online.
Tertullian, "Of Patience" - An early Christian account of patience.
Gregory the Great, Forty Gospel Homilies - I draw considerably from Gregory's ideas about patience in Homily 35. (I will continue to search for some online version of that particular text. If you can read Latin, you can check out Homily 35 here.)
Seneca, On Anger - Included in this online version of Seneca's essays. (A better translation is the one in Kaster and Nussbaum's Anger, Mercy, Revenge.)
Shantideva, A Guide to the Bodhisattva's Way of Life - Chapter 6 offers an influential Buddhist perspective on patience, with an emphasis on patient tolerance.
Franz Kafka, The Zürau Aphorisms - an obscure notebook of Kafka's where I discovered a couple intriguing remarks on patience, here with critical commentary on translation and content by Michael Cisco. An interesting little book. (I've linked to #2; see also #3 for more of Kafka's succinct ideas about patience.)
MORE LINKS COMING SOON!