What are good resources for a beginner, non-computer genius type of person, to learn Plain TeX?

Grab a copy of TeX for the Beginner, by Wynter Snow. It teaches basics of Plain TeX programming and has notes for LaTeX users explaining key differences and how to implement similar features. Additionally, browsing through the Plain TeX contributions directory of CTAN may give you some useful code to learn from.

another good possibility is "a gentle introduction to tex" by michael doob. available from ctan: http://www.ctan.org/pkg/gentle (and included in tex live: texdoc gentle).

there are a few others listed on the ams web page http://www.ams.org/tex/tex-pub under "plain tex -- beginner to intermediate". links are given where available. unlike some other books listed on that page, the publishers have kept most of the "beginner" selections in print, paper only, at rather high prices. (when victor eijkhout's "tex by topic" went out of print, he negotiated with the publisher to revert the rights to himself, and released it for free access. too bad that's apparently not possible for these.)

The secretary for my research group learned TeX from The TeXbook. So did I and everyone else in the research group (students, postdocs, profs, and secretaries) up until the last 5 or 10 years. In those recent years, I don't think I have met a single person who wanted to learn TeX, so I don't know much about recent books.

Maybe some of the recent books are wonderful, and probably the advice given previously is excellent. But I know a lot of people who learned from Knuth's book, and I've noticed that anyone who spends the hour it takes to "get into the groove" of the book tends to find it very clear and surprisingly engaging. Therefore, I recommend this classic without reservation.

The TeXbook by Donald E. Knuth (Reading, Massachusetts: Addison-Wesley, 1984), x+483pp. ISBN 0-201-13448-9