Medieval

The sections here are divided by the area where the text was written, the categories are: African, European, Middle Eastern and the Americas.

Authors who contributed more than one work include: Pope Urban II, Moses Maimonides, Francis of Assisi and Thomas Aquinas.

A general timeline has been provided here.

African

Mishneh Torah by Moses Maimonides (Between 1170 and 1180)
Guide for the Perplexed by Moses Maimonides (Circa 1190)
History of the Patriarchs of Alexandria (Circa 1250 AD)
Kebra Nagast / The Glory of the Kings (1300's--in it's present form)

Of the Americas

The Great Law of Peace/the Iroquoian Constitution (Around 1100 to 1450)

Asian

Wujing Zongyao / Collection of the Most Important Military Techniques (Circa 1040)
Poems by Lu Bai (720-762 AD)
Romance of the Three Kingdoms by Luo Guanzhong (1300's)

European

The Ruin of Britain by Gildas (500)
Against Eutyches and Nestorius by Boethius (513) 
The Consolation of Philosophy by Boethius (523)
The Trinity by Beothius (Circa 523)
Beowulf (Circa 700-1000)
The Ecclesiastical History of the English People by Venerable Bede (731)
Bede's Death Song (735)
Historia Brittonum by Nennius (Circa 828)
The Song of Roland (Circa 1050)
Call for the First Crusade by Pope Urban II (1095)
Letter from Pope Urban II (December, 1095)
Erec and Enide by Chretien de Troyes (Circa 1170)
Cligès by Chrentien de Troyes (Circa 1176)
Yvain, the Knight of the Lion by Chretien de Troyes (Circa 1180)
Lancelot, the Knight of the Cart by Chretien de Troyes(Circa 1180)
Prtceval, the Story of the Grail by Chretien de Troyes (Circa 1190)
Nibelungenlied (Circa 1200)
Magna Carta (1215)
Francis of Assisi's Letter to All Christians (1215)
Canticle of the Sun by Francis of Assisi (Circa 1224)
Parzival by Wolfram Von Eschenbach  (Circa 1225)
Contra Gentiles by Thomas Aquinas (1264)
The Tale of Igor's Campaign (1185-1300)
Summa Theologica by Thomas Aquinas (1274) 
The Travels of Marco Polo (Circa 1300)
The Divine Comedy by Dante Alighieri (1314)
The Decameron collected by Giovanni Boccaccio (1353)
Vision of Pier`s Plowman (Circa 1390)
The Canterbury Tales by Geoffrey Chaucer (Circa 1400)
A Journey Beyond Three Seas by Afanasii (1475)
Le Morte D`Arthur by Thomas Malory (1485)

Middle-Eastern

The Qu'ran

Mywatta Malik (795)
Sahih al-Bukhari (870)
Sahih Muslim (875)
Sunan Ibn Majah (887)
Sunan Abi Dawud (888)
Jami' at-Tirmidhi (892)
Sunan an-Nasa'i (915)
The Epic of Kings by Ferdowsi (Circa 1010)
The Gulistan of Sa'di (1258)

Rihla / The Journey (Not yet available for free)