letter-plain – Letter macros for Plain TeX
These macros would seem to be used by Knuth himself (a version with a slightly different default address may be found in the CTAN copy of Knuth’s “local library” of macros).
Export the package reference as BibTeX file
Maybe you are interested in the following packages as well.
- bellmac: Outline scheme for form letter production
- toc-zar: Plain TeX table of contents macros
- histyle: A "HighStyle" environment for TeX
- resumemac: Plain TeX macros for resumés