I just became aware that this seminal paper by John Reynolds was republished by HOSC in 1998, making it available online. (Thanks, Olivier and Carolyn!) If you've never read it and you are interested in programming languages then I suggest you read it immediately. It introduced the term metacircular interpreter and the concept of defunctionalization, as well as being one of the first clear explanations of continuation passing style. The paper is accompanied by a new forward written by John, Definitional Interpreters Revisited.
Oleg Paraschenko has typed in all the examples from The Essence of Functional Programming, and made them available online. There is also a review of the paper in Russian. Thanks, Oleg!