Common coins of the mid-4th century with text “FEL TEMP REPARATIO” – an interesting site by Doug Smith discusing coins introduced as part of the coinage reform of 348 AD by Constantius II and Constans. All coins of this reform bear the reverse legend FEL TEMP REPARATIO (‘Restoration of Happy Times’). Also see Doug’s Review of Late Roman Coins
Coins of Constantine – House of Constantine Bronzes
Victor Clark has an interesting site on the coins of Constantine the Great, with some additional Constantine family coins illustrated as well.
Doug Smith has some good material on Constantinian period coins.
The section of Joe Sermarini’s Numiswiki on Constantinian era coins includes good information and photos. – Useful portraits for coin identification.
Steve Niederloh’s Celator’s Art site has good material for beginning collectors; one of his main collecting areas being the family of Constantine.
Voz’s page on Tetrarchy coins. (285-324 CE)
Bill Welch has an interesting page on Sol and Oriens.