macmarkdown
I would like to be able to pop up a window on my Mac displaying a rendered HTML preview of selected text (ideally a completely chromeless window like that used by QuickLook, but an ordinary Web browser window could work if necessary, but the less chrome the better).
What tools are available to do this?
My solution to mapping keyboard shortcuts to arbitrary services (as well as general workflows, application launches and scripts) is FastScripts.
Try it for free and pay if you feel you can or need more than 10 shortcuts to be active at the same time.
md2key is exactly what you want. md2key is an open source tool for converting markdown to Keynote presentations.
Install md2key with the command:
gem install md2key
md2key markdown.md
Best Answer
I tried a few things (even a websocket node app I wrote) to do this, however I found an app, Marked, that does exactly what you asked. It constantly reads a text file and shows you HTML/MD on the fly as you type. It's pretty nifty, commercial, but nifty.
The Marked Bonus Pack comes with a service for previewing text selections.