A very useful blog post at http://sixthform.info/steve/wordpress/?p=59 tells us about a variety of options available on the internet for using LateX online. The websites usually have a TeX renderer running on the server side which spits out the mathematical equations generated from the input [LaTeX]. I liked two of them.

1) Processing complete LaTeX

http://nirvana.informatik.uni-halle.de/~thuering/php/latex-online/latex.php

I am sharing what I liked about these sites. The first one uses sessions to maintain the output file. You can paste/write a LaTeX source in the textbox, and obtain the output as PS, PDF, DVI or PNG. A sample LaTeX code which you will provide as input will look like this

\documentclass[12pt]{article}
\title{\Sample}
\date{}
\begin{document}
  \maketitle
  \begin{eqn}
    Here's an equation: \sum_a^b f^2(x) = 0
  \end{eqn}
\end{document}

If you want the English edition for the first link, add the sprachauswahl parameter with value 2, i.e., http://nirvana.informatik.uni-halle.de/~thuering/php/latex-online/latex.php?sprachauswahl=2

2) Processing only the equations

http://www.codecogs.com/components/equationeditor/equationeditor.php

The second link is tailor made for embedding equations on a webpage, in the form of an image. It doesn’t process a whole LaTeX code, but it will compile the LaTeX code, as if between the \begin{eqn} and \end{eqn} tags. The image which is generated has the URL of the form

http://www.codecogs.com/eq.latex?\sum_{a}^{b} f^2(x)

The site provides a clean look and nice tools (a set of toolbar implemented in JavaScript) to assist the user.

Sidenote

As a sidenote, to render MathML (offline) using the JEuclid library, download jeuclid-core-3.0.4-SNAPSHOT.jar, commons-logging-1.1.jar, jeuclid-mathviewer-3.0.4-SNAPSHOT.jar from http://jeuclid.sf.net/jeuclid-webstart/ (append filename to this URL) and run the net.sourceforge.jeuclid.app.MathViewer class. For windows, you will invoke something like the following:

java.exe -classpath jeuclid-core-3.0.4-SNAPSHOT.jar;commons-logging-1.1.jar;
jeuclid-mathviewer-3.0.4-SNAPSHOT.jar;./  net.sourceforge.jeuclid.app.MathViewer

It has a simple GUI which takes the input as a file.