You can use latex in forums and blog posts. See documentation here: http://docs.mathjax.org/en/v1.1-latest/index.html

There are some custom functions you can use, for example:

\$\ket{\psi}\$ gives $\ket{\psi}$

Here is current custom functions:

%%%%%Shorthand symbols
\DeclareMathOperator*{\argmin}{\arg\!\min}
\newcommand{\tr}{\operatorname{Tr}}
\def\avg#1{\mathinner{\langle{#1}\rangle}}
\def\bra#1{\mathinner{\langle{#1}|}}
\def\ket#1{\mathinner{|{#1}\rangle}}
\newcommand{\braket}[2]{\langle #1|#2\rangle}
\newcommand{\proj}[1]{\ket{#1}\!\!\bra{#1}}
\newcommand\R{{\mathrm {I\!R}}}
\newcommand\N{{\mathrm {I\!N}}}
\newcommand\h{{\cal H}}
\newcommand\V{{\cal V}}
\newcommand\p{{\sf p}}
\newcommand\w{{\sf w}}
\newcommand{\qed}{$\hfill \Box$}
\newcommand\diag{{\mbox{diag\,}}}
\def\half{\tfrac{1}{2}}
\newcommand{\ignore}[1]{}
\newcommand{\ra}{{\rightarrow}}
\newcommand{\be}{\begin{equation}}
\newcommand{\ee}{\end{equation}}
\newcommand{\ba}{\begin{eqnarray}}
\newcommand{\ea}{\end{eqnarray}}