LaTeX - Online Resources

Here is a personal list of helpful online resources out of the CTAN (ctan.org) but all about (La)TeX and its friends.

Must Know Sites

CTAN (The Comprehensive TeX Archive Network)
Like CPAN (P stands for "Perl") and CRAN (R stands for programming language "R"), CTAN is a central place for all kinds of material around TeX.
Q & A sites
- TeX - LaTeX Stack Exchange, nicknamed as TeX-SX
- LaTeX Community, a somewhat more traditional site
Overleaf, an online editor, compiler, and project manager
Overleaf has joint forces with ShareLaTeX since Jun 2017, and the two sites now provide the same service, called overleaf v2.

Online Documentations

Short Guides

For basic uses, some guidelines of MathJax can be a good learning resource of LaTeX math formula.

(MathJax Guides) LaTeX math in less than 10 minutes shows juicy examples, both carefully classified and interactively displayed, made with love by Quora user Gilles.
(MathJax Guides) MathJax basic tutorial and quick reference from Mathematics Stack Exchange, provides more complete reference as well as more complex examples.

FAQ

The TeX Frequently Asked Question List, used to be the UK FAQ

Full-Length Books

Dickimaw's 3-volume LaTeX books

Useful Tools

Symbol recognizer
Draw desired (math) symbols and receive suggestions about symbol appearance, respective LaTeX command, and relied package.
Table generator
Draw tables as using MS Office, and export output in LaTeX codes.
Commutative diagram editor
Draw commutative diagram interactively with multiple kinds of arrows, and export it as LaTeX codes based on package tikzcd.
Chemical molecules editor
Input with mouse, name of compound, or mol format, and get chemical molecules in PDF, LaTeX package chemfig, or mol format.

Collections

Collections of TikZ examples
Collections of LaTeX templates, also called LaTeX classes

Similar Lists

Useful Links, a webpage maintained by official LaTeX Project
Related sections of documentation (PDF format) of LaTeX package docsurvey, a survey focused on programming-related documentation for LaTeX

Specific Resources for Chinese Users and among CJK Characters handling

Q & A sites
- CTEX Community, a site for Chinese TeX Community
- LaTeX Topic of zhihu.com, a Chinese version of Quora-like site
- GitHub issue part of package collection ctex-kit