There are numerous original sources below. Read (or for longer ones, skim or partially read) at least one original source and engage in Idea Mining.
(If you are unfamiliar with Idea Mining, please read the linked page -- it is somewhat different than Sentences About)
There's plenty of ideas to be mined in the articles specifically about teaching machines, but feel free to roam to other subjects and articles if they are pertinent.
For people looking for that obscure conference document feeling, we have Trends in Programmed Instruction, the conference proceedings from the first annual conference of the Society for Programmed Instruction. Unfortunately this is a big hunk of PDF but it has the advantage that there are dozens of short articles inside.
New Methods and Aims in Teaching is a short 1964 article by B. F. Skinner written for a general audience.
Teaching Machines, the Article is less fun than Teaching Machines, the event. But it's the article that started it all, except for Pressey. And the other Skinner. Published in Science, but written in style of a popular treatment.
Has Gertrude Stein a Secret? is an Atlantic Monthly article by Skinner which features a Ouija board reference.
The Uses of Computers in Education a 1968 Scientific American article about Patrick Suppes's work at Stanford, by Patrick Suppes.
Are Theories of Learning Necessary? a 1950 article by B. F. Skinner. Very involved, but great for participants looking for a challenge, and relevant in our "post-theory" Age of Data.
A Case History in Scientific Method is another lengthy Skinner read, but makes a good skim too.