Examples of powerful LaTeX packages and techniques in use — a great way to learn LaTeX by example. Search or browse below.

Figures TikZ du cours "POSTULATS DE LA DYNAMIQUE"
Ce document regroupe les codes TIKZ des figures utilisées pour le cours "POSTULATS DE LA DYNAMIQUE" situé à la page http://femto-physique.fr/mecanique/meca_C2.php
Jimmy Roussel

Figures TikZ du cours "PROBLEMES E CHUTE"
Ce document regroupe les codes TIKZ des figures utilisées pour le cours "PROBLEMES DE CHUTE" situé à la page
http://femto-physique.fr/mecanique/meca_C3.php
Jimmy Roussel

LaTeX Bibliography Example: The natbib Package
The natbib package provides automatic numbering, sorting and formatting of in text citations and bibliographic references in LaTeX. It supports both numeric and author-year citation styles.
The natbib package is the most commonly used package for handling references in LaTeX, and it is very functional, but the more modern biblatex package is also worth a look.
writeLaTeX

RH Workshop Example 1
Riget Workshop example 1. Minimal document showing off text formatting
Timo Röder

Tikz UML2 Activity Diagram and Mathematical Block Diagram
Tikz Example for UML2 Activity Diagram and Mathematical Block Diagram
Martin Hünermund

Table with formulas and footnotes
This is a table I used in the paper W. Li, G. Wei, D. Ding, Y. Liu and F. E. Alsaadi, "A New Look at Boundedness of Error Covariance of Kalman Filtering," in IEEE Transactions on Systems, Man, and Cybernetics: Systems, vol. 48, no. 2, pp. 309-314, Feb. 2018. I would like to share some LaTex codes for the table which might be helpful to some readers.
Wangyan Li

Minipage para evitar dividir item em páginas
Exemplo criado para a pergunta no SOPT: http://pt.stackoverflow.com/questions/69338/como-evitar-que-item-iniciado-numa-pagina-continue-em-outra-em-latex
Luiz Carlos Vieira

Draw by MetaPost with LuaTeX and luamplib in Japanese
Test paper for Japanese TeX and MetaPost User
Satie Moonlight

LTP in Synapse
Long Term Potentiation (LTP) in synapse.
Dilawar Singh