I've been reading various speeches and works by Cicero, and while reading On the Ideal Orator, I was wondering whether any other philosophers (especially relatively contemporary ones) also wrote on the subject. Not asking for theories on the subject, just names of writers/writings.
Here are a few other things to checkout, mostly not at all modern:
Aristotle's Rhetoric is one obvious example on the subject itself.
Other works of Cicero, while perhaps not addressing oration in the content, are themselves considered useful examples of oration. See Pro Archia Poeta as an example. The Wikipedia article discusses (and I've seen other similar discussions in introductions to book versions that concur) how the speech is structured.
Augustine was trained as a rhetorician before his conversion, so addresses rhetoric and oratory in some of his works. I'm not sure of any work that addresses rhetoric at length itself, but he discusses his education in Rhetoric in The Confessions and in all his works follows similar patterns based on his earlier training. He studied Cicero extensively and states explicitly that Cicero was an influence on him, so any of his writings are going to have a rhetorical style similar to Cicero's.
The speeches in Thucydides might also be interesting. He doesn't write anything theoretical about rhetoric, but he says himself that the speeches are largely what the speakers should have said, and so in that sense are an applied guide to oration.
A list of more modern theorists of rhetoric, Wikipedia has a list. I can't say I've read any of them though.
Chaim Perelman was a philosopher of law, who studied, taught, and lived most of his life in Brussels. He was among the most important argumentation theorists of the 20th century. His chief work is the Traité de l'argumentation - la nouvelle rhétorique (1958), with Lucie Olbrechts-Tyteca, which was translated into English as The New Rhetoric: A Treatise on Argumentation, by John Wilkinson and Purcell Weaver (1969). Perelman and Olbrechts-Tyteca move rhetoric from the periphery to the center of argumentation theory. Among their most influential concepts are "dissociation," "the universal audience," "quasi-logical argument," and "presence."
Kenneth Burke was a rhetorical theorist, philosopher, and poet. Many of his works are central to modern rhetorical theory: A Rhetoric of Motives (1950), A Grammar of Motives (1945), Language as Symbolic Action (1966), and Counterstatement (1931). Among his influential concepts are "identification," "consubstantiality," and the "dramatistic pentad." He described rhetoric as "the use of language as a symbolic means of inducing cooperation in beings that by nature respond to symbols." In relation to Aristotle's theory, Aristotle was more interested in constructing rhetoric, while Burke was interested in "debunking" it.
Edwin Black was a rhetorical critic best known for his book Rhetorical Criticism: A Study in Method (1965) in which he criticized the dominant "neo-Aristotelian" tradition in American rhetorical criticism as having little in common with Aristotle "besides some recurrent topics of discussion and a vaguely derivative view of rhetorical discourse." Furthermore, he contended, because rhetorical scholars had been focusing primarily on Aristotelian logical forms they often overlooked important, alternative types of discourse. He also published several highly influential essays including: "Secrecy and Disclosure as Rhetorical Forms.", "The Second Persona," and "A Note on Theory and Practice in Rhetorical Criticism."
Marshall McLuhan was a media theorist whose theories and whose choice of objects of study are important to the study of rhetoric. McLuhan's famous dictum "the medium is the message" highlights the significance of the medium itself. No other scholar of the history and theory of rhetoric was as widely publicized in the 20th century as McLuhan.
I.A. Richards was a literary critic and rhetorician. His The Philosophy of Rhetoric is an important text in modern rhetorical theory. In this work, he defined rhetoric as "a study of misunderstandings and its remedies," and introduced the influential concepts tenor and vehicle to describe the components of a metaphor—the main idea and the concept to which it is compared. The Groupe µ. This interdisciplinary team has contributed to the renovation of the elocutio in the context of poetics and modern linguistics, significantly with Rhétorique générale (1970; translated into English as A General Rhetoric, by Paul B. Burrell et Edgar M. Slotkin, Johns Hopkins University Press, 1981) and Rhétorique de la poésie (1977).
Stephen Toulmin was a philosopher whose models of argumentation have had great influence on modern rhetorical theory. His Uses of Argument is an important text in modern rhetorical theory and argumentation theory.
Richard E. Vatz is a rhetorician responsible for the salience-agenda/meaning-spin conceptualization of rhetoric, later revised (2014) to an "agenda-spin" model, a conceptualization which emphasizes persuader responsibility for the agenda and spin he/she creates. His theory is notable for its agent-focused perspective, articulated in The Only Authentic Book of Persuasion (Kendall Hunt), derived from the Summer, 1973 Philosophy and Rhetoric article, "The Myth of the Rhetorical Situation."
Richard M. Weaver was a rhetorical and cultural critic well known for his contributions to the new conservatism. He focused on the ethical implications or rhetoric and his ideas can be seen in "Language is Sermonic" and "The Ethics of Rhetoric." According to Weaver there are four types of argument, and through the argument a person habitually uses the critic can see the rhetorician's worldview. Those who prefer the argument from genus or definition are idealists. Those who argue from similitude see the connectedness between things and are used by poets and religious individuals. The argument from consequence sees a cause and effect relationship. Finally the argument from circumstance considers the particulars of a situation and is an argument preferred by liberals.