AMS: TeX-Related Publications: Some TeX-related publications grouped by level of TeX expertise or subject area.
Baskerville: Publication of the UK TUG archived on CTAN in source form and PDF format.
Eutupon: The official forum of the Greek TeX Friends Group, published electronically in Greek and English.
Knuth: Computers and Typesetting: Don Knuth's page for the TeXbook, METAFONT book and the Computers and Typesetting set. Errata and procedures for reporting bugs and mistakes.
Making TeX Work: A book about using TeX and the complete TeX environment. Written by Norman Walsh and (re)published under the GNU Free Documentation License.
The PracTeX Journal: Dedicated to the exchange of practical experience and instruction of the use of TeX and other TeX-related or TeX-derived systems.
The TeXbook: Publisher's page for the TeXbook at Addison-Wesley. On-line ordering.
TUGboat: Communications of the TeX Users Group (TUG). PDF versions of those articles for which the authors have agreed to electronic publication. Articles posted to CTAN as part of a macro package are linked to the CTAN source, others in PDF. Articles are not posted until a year after publication.
Wikibooks: TeX: A collaboratively written guide to the basic engine for macro languages (formats) as Plain TeX, LaTeX and Context.