Generally useful sites:
One of the most invaluable sites on the web for anyone interested in ancient Rome is Lacus Curtius. It has complete texts of many Roman authors in Latin and English – and Greek authors in Greek and English – and essays on various topics; I am seriously in awe of the work that has gone into this site. It has a copy of Platner and Ashby’s invaluable 1929 (frequently linked on this site) Topography of Ancient Rome.
Digital reconstructions of Rome.
a. Rome Reborn. Admittedly not nearly as useful as it used to be since they took the Rome Reborn layer from Google Earth, it still has some impressive digital reconstructions of ancient Rome. Unfortunately, it’s an incredibly clean and rather unlived in looking Rome so it makes it hard to think of it as a lived in city.
b. This is a really interesting discussion of using virtual crowds in the Colosseum to look at crowd movement.
Further reading: the following is a selection of books and articles on Roman spectacles that I think are particularly interesting, accessible, or useful:
D.L. Bomgardner’s Story of the Roman Amphitheatre is a good discussion of the Colosseum and the other amphitheatres of the Roman world. His introduction is a good review of the history of the games as well.
Anything by Kathleen Coleman, but especially “Fatal charades: Roman executions staged as mythological enactments”, Journal of Roman Studies 80 (1990), 44–73, “Launching into history: aquatic displays in the early Empire”, Journal of Roman Studies 83 (1993), 48–7″ and “Missio at Halicarnassus” Harvard Studies in Classical Philology 100 (2000), 487-500.
Garett Fagin, The Lure of the Arena. (Cambridge University Press, 2011). A fascinating and accessible look at why the Romans enjoyed violent and bloody spectacles, which uses various theories of social and crowd psychology to explore why people enjoy looking at disturbing events in groups. Highly recommended.
Alison Futrell. The Roman Games. (University of Texas Press, 2001). A handy sourcebook on the games with useful commentary and context.
Greek sports and spectacles
This is a good site on the ancient Olympics.