Texify
Enter a bit of LaTeX on this site, and it’ll give you a permalink to a GIF-rendering of your equation. For example:

2 Comments RSS · Twitter
November 28, 2007 9:24 PM
You can use Mac OS X's Grapher application to do some very similar stuff.
Enter and expression in Grapher, then right-click it to copy as TIFF, EPS, PDF, or text. You can even copy an expression as LaTeX!