Quickly pow is a small tool written by 37 Signals , that allows you to quickly set up Rack based applications and give them a url without any need for apache , nginx , etc or altering you host file.
With a few alterations to your Jekyll site you can get it to work with pow as well. You are going to need to install pow if you haven't done so already full instructions can be found at pow.cx
now alter your Jekyll apps gemfile and add
next you will need a config.ru file to allow pow to start your jekyll server , create one at the root of your jekyll site and add
and finally cd to .pow directly in your home directory and create symlink for your new Jekyll site
ln -s /path/to/your/jekyllsite
Now you can open your browser and visit <folder>.dev for example jeykllsite.dev and your done