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

Matikkatreeni
Perusanalyysi.
Rodion Efemov

LaTeX Coffee Stains
This package provides an essential feature to LaTeX that has been missing for too long. It adds a coffee stain to your documents. A lot of time can be saved by printing stains directly on the page rather than adding it manually. You can choose from four different stain types.
Hanno Rein, Evan Sultanik, Luis Randez, Adrian Robson

Formatos en \LaTeX
Article format for authors, revista ingeniería y ciencia
ingenieria y ciencia

Mémoire de Séries Temporelles
Séries temporelles
LaurentLesage

Simple Draft Manuscript Template with Line Numbers
Simple template for generating drafts of papers and articles with line numbers.
Daniel Rothenberg

French letter
Typing an official letter in French.
Guillaume Bouvier

Questionnaire
A questionnaire example.
Antonette

Using fancyhdr for Custom Page Header and Footers in a Two-sided Document
A simple example demonstrating how to put texts at different locations of the headers/footers using fancyhdr.
LianTze Lim

A Simple Example for ME EN 575
A basic starter example to help students see examples of useful packages, math environments, figures, subfigures, tables, etc.
Andrew