festival of Jupiter -- all ides were sacred to Jupiter
Rite of the 'October Horse' -- one of the many rituals which makes the study of Roman religion so fascinating. On this day a race between two-horse chariots would be held in the Campus Martius, and the right hand horse of the victorious pair would be sacrificed by the flamen of Mars on an altar (in the Campus Martius, of course). After the sacrifice, people who lived in the Via Sacra neighbourhood would fight the people who lived in the Suburra for the right to the head. If the 'via sacranites' won, they'd display it on the Regia; if the Suburranites won, it would be displayed at the Turris Mamilia. Meanwhile, the cauda (tail - genitals) would be rushed to the Regia so the blood would drip on the sacred hearth; the Vestal Virgins also probably kept some of the blood for use at the Parilia on April 21.
ludi Capitolini -- a somewhat obscure day of games which was unique in its not being 'public' (in the sense of being put on by a magistrate) but rather the ballywick of a collegium of 'Capitolini'. Not much is known about what went on at these games save that an old man wearing the bulla of of a young boy was paraded about and mocked; there were possibly competitions in boxing and running as well.
55 B.C. -- death of Lucretius
70 B.C. -- birth of Publius Vergilius Maro, a.k.a. Vergil, a.k.a Virgil
1999 -- death of Don Fowler, fellow of Jesus College, Oxford and frequent contributor to the Classics list almost from its inception, among other things, of course