Often you want to test out some simple static http / css / js code in your local environment. You could setup mass virtual hosting and dnsmasq with a wildcard domain to serve *.dev, but for purely static files, I find this is an easier setup. And there is less overhead, as pow spins up nodejs to serve a request rather than constantly having apache run in the background.
Pow is a zero-configuration Rack server for Mac OS X. You can install it with homebrew
brew install pow
And then follow the instructions brew prints out
sudo pow --install-system
pow --install-local
Powder is a gem which enables easy control of pow. To install,
gem install powder
Now create a directory which contains a public directory and an index.html file, and use powder to configure pow to serve the directory.
mkdir -p test/public
vim test/public/index.html
# add html content
powder link
Now load http://test.dev in your browser, and you should see the content of the index.html file loaded