I love this idea and I had this plugin several years ago, but it was always a bit slow and buggy so I rarely used it. Can anyone vouch for its improvement?

People in this thread may be interested in socrates

http://socrates.io/

It does instant Markdown and LaTeXing in the browser. It's hyperlink-shareable, with no plugin required, so you don't have to ask your collaborator to install anything. Just send them the URL and they can instantly see your equations and edit it.

Socrates has been my preferred method of sharing a bit of math with someone when it's too complex to just write as text in an email, and not complicated/important enough to justify latex'ing up a document.

Also, if you just want to share a single equation as an image, try Roger's Online Equation Editor

http://rogercortesi.com/eqn/

How do you get socrates.io to do latex? I could only figure out how to do markdown.

With $$ $$

Amazing. This could make communicating with professors over email so painless!

http://mathb.in has worked really well for me.