Thanks to the Mathtex server at Forkosh's MathTeX website, you can instantly render simple LaTeX expressions below. This is useful for quick-and-dirty conversion of, say, LaTeX that your TA sent you in an email ;-) . I'm actually using the server at problem-solving.be now, but the HTML for this form was taken from the forkosh site.
... and click "Submit Expression" to see it rendered here