<p>Here are some options that I know of:</p>
<ul>
<li>There is a CV <a href="https://stats.stackexchange.com/editing-help">help page</a> for the markdown options that the site supports.  That covers things like italics, and some (but very little) actual <span class="math-container">$\LaTeX$</span>.</li>
<li>There is a comprehensive 'tutorial' thread on <a href="https://math.meta.stackexchange.com/">meta.Mathematics</a> here: <a href="https://math.meta.stackexchange.com/q/5020">MathJax basic tutorial and quick reference</a>.</li>
<li>One way to learn is to find something that uses <span class="math-container">$\LaTeX$</span> that you would like to also be able to do and right-click on it.  Then select <code>Show Math As -&gt; TeX Commands</code>, and it will display the code that was used to create it.</li>
<li>If you need to identify the <span class="math-container">$\LaTeX$</span> name / code for a symbol and you can draw it, <a href="http://detexify.kirelabs.org/classify.html" rel="nofollow noreferrer">detexify</a> might help.</li>
<li>Stack Exchange does have a <a href="https://tex.stackexchange.com/">Q&amp;A site dedicated to TeX</a>; that might be helpful as well.</li>
<li>After that, it's the broader internet; I've found <a href="http://www.onemathematicalcat.org/MathJaxDocumentation/TeXSyntax.htm" rel="nofollow noreferrer">this MathJax documentation site</a> to be very comprehensive and informative, but it's <em>really</em> slow to load.  <a href="https://web.archive.org/web/20140110233329/http://web.ift.uib.no/Teori/KURS/WRK/TeX/symALL.html" rel="nofollow noreferrer">This webpage discovered by @Andre</a> is less extensive, but loads <em>much</em> faster.  There's a handy 'reference card' <a href="https://web.archive.org/web/20160304012339/http://elevatorlady.ca/doc/refcard/expressions.html" rel="nofollow noreferrer">here</a>.</li>
<li>Lastly, I suppose you could ask a question about how to do something specific here (e.g.: <a href="https://stats.meta.stackexchange.com/questions/1419/">latex-macros-for-expectation-variance-and-covariance</a>).</li>
</ul>
