I will collect here a list of supplementary resources which you may find helpful, especially if you are building your posterboard.
First of I would like to call your attention to an excellent online resource: MacTutor. This should be a helpful supplement to your reading. One good way to use this resource is to find the biography of someone mentioned in the text, and follow the trail of hyperlinks that connects this person to other mathematicians. This site also allows you to browse articles organized by subject, or to study the events and personalities of a particular age.
For a long list of online resources, or for answers to specific questions, there is rarely a better place to start than Google. In particular if you click on the "Directory" tab at Google and type history mathematics into the search box you will find more online resources than you thought could possibly exist.
The idea of a spacetime posterboard is inspired by the famous spacetime diagram drawn by Otto Neugebauer. The full diagram can be found on page 2 of A History of Mathematics, second edition, by Boyer and Merzbach. I have reproduced a fragment of it here, along with some questions to ask yourself when building your own.
Here are some of the dynasties, events, and personalities that should probably be included in your posterboard in order to frame the mathematical events we will study. I will add to this list as the semester progresses.
Egypt's Old, Middle, and New Kingdoms. The alphabet. Assyrian Empire. First and Second Babylonian Empires. Hittites. Scythians. Lydians. Medes. Persian (Achaemenid) Empire. Jews freed from Babylon. Hatshepsut. Ramesses II. Hammurapi. Cyrus the Great. Akhenaten. Stonehenge. Pyramid of Cheops (Khufu). Parthenon. Angkor Wat. Taj Mahal. Ahmes (Rhind) papyrus. Moscow mathematical papyrus. Plimpton 322. Trojan War. Homer. Peloponnesian War. Pythagoras. Thales. Theaetetus. Eudoxus. Euclid. Archimedes. Hypatia. Discovery of incommensurables. Quadrature of the lune. Method of exhaustion. Plato's Academy. Library at Alexandria. House of Wisdom. Euclid's "Elements". Apollonius "Conics". Diophantus "Arithmetica". Ptolemy's "Almagest". Alexander the Great. Maccabees. Seleucids. Ptolemies. Punic Wars. Hannibal. Julius Caesar. Cleopatra. Destruction of the Temple in Jerusalem (twice). Buddha. Socrates. Jesus. Zarathustra. Mani. Augustine of Hippo. Muhammad. Thomas Aquinas. Guru Nanak Dev. Martin Luther. John Calvin. Baha'u'llah. Vedic Period. Mauryan Empire. Ashoka. Parthian Empire. Sassanid Empire. Kushan Empire. Huns defeat Rome. Attila. Huns conquer India. Guptan Dynasties. Chola Empire. Chalukyan Kingdom. Pallava Dynasties. Mahmud of Ghazni. Muhammad Ghuri. Vijayanagara Empire. Bahamani Kingdoms. Delhi Sultanate. Mughul Dynasty. Aryabhata. Brahmagupta. Bhaskaracharya. Mahavira. Chakravala. "Sulvasutras". Bakhshali manuscript. Earliest decimal inscriptions. Decimal numbers adopted in Syria. Decimal fractions developed in Baghdad. Decimal fractions adopted in India. Paper invented in China. Paper adopted in India. Paper adopted in Europe. Printing invented in China. Printing adopted in Europe. Constantine the Great. Nicene Council. Byzantine Empire. Visigoths. Vikings. Islamic Empire. First Umayyad Caliphate. Abassid Caliphate. Fatamid Caliphate. Second Umayyad Caliphate. Crusades. Ottomam Empire. Safavid Dynasty. Al-Khwarizmi. Al-Karaji. Ibn al-Haytham. Al-Khayyami. Nasir al-Din. Sharaf al-Din. Al-Samaw'al. Al-Biruni. Thabit ibn Qurra. Ibn al-Baghdadi. Avicenna. Averroes. Spanish wars of reconquista. Roman inquisition. Spanish inquisition. Jews expelled from Spain. Charlemagne. Genghis Khan. Kublai Khan. Tamurlane. Babur. Ibn Battuta. Marco Polo. Mehmet captures Constantinople. Columbus sails to America. Venerable Bede. Fibonacci. Plague spreads thru: China; Russia; the Middle East; Europe. Modern symbols for: equality; inequalities; arithmetic operations; exponents; radicals; common fractions; decimal fractions. Gregorian calendar. Paciolo. Del Ferro. Cardano. Ferrari. Complex numbers discovered. Quaternions discovered. Viète. Regiomontanus. Stevin. Brahe. Kepler. Copernicus. Galileo. Descartes. Fermat. Pascal. Hooke. Huygens. Newton. Leibniz. Voltaire. Bernoulli family. Euler. Mercator projection. Logarithms. Fermat's "Last Theorem" stated. Fermat's "Last Theorem" proved. American independence. French revolution. Napoleonic empire. Metric system. Smith's "Wealth of Nations". Marx' "Das Kapital". Darwin's "Origin of Species".
Recommended reading: The Art of Algebra from al-Khwarizmi to Viète: a Study in the Natural Selection of Ideas, by KH Parshall. I am not sure whether natural selection (in the sense of Darwin) is really an accurate description of how mathematical ideas are adopted, however the case she studies has a lot to teach.