Update: because the showdown.js link is dead, I've created a github repo for this.
Introducing QuickSlides: Quick and Dirty Presentations in Markdown using Slidy and Showdown.
git clone git@github.com:airportyh/QuickSlides.git name
where name is the directory name you want for your presentation.
Then, edit presentation.html and write your slides in Markdown within the blog comments powered by Disqus