Detexify LaTeX. Want a Mac app?
Lucky you. The Mac app is finally stable enough. LaTeX Lab. LaTeX project: LaTeX documentation. This page contains references to documentation that is available on the net.
Most of these are in English but there is a section on non-English documentation. They are by both the LaTeX team and other contributors. Also, there's a whole page dedicated to books on LaTeX and related topics. If you know about a list of TeX and related documentation not listed here, please contact webmaster@latex-project.org. Documentation distributed with LaTeX.