this November 1962 interview in the now defunct The Realist by Paul Krassner, primarily about Heller's 1961-released Catch-22. Several pages long, fascinating, funny, often over my head, enlightening—including on the origin of the name "Yossarian" (it was meant to be from "an extinct culture, somebody who could nto be identified either geographically, or culturally, or sociologicaly..."). Haven't finished it yet, but I will soon—and I'm counting on it making me smarter, damnit.
Update, March 2015:
The link disappeared. I've replaced it. You have to jump to page 46 (use numbers up top) to get to the second page of the interview, and go on from there.