Online LaTEX editor

http://www.codecogs.com/latex/eqneditor.php

Awesome! Now I can practice writing LaTeX : o )

For example, here's (modified) code to write a function, via John D. Cook:


T(n) =
\left\{
\begin{array}{ll}
2  & \mbox{if } n = 2\mbox{ }, \\
2T(n/2)+n & \mbox{if } n = 2^k \mbox{ , for } k > 1
\end{array}
\right.