itunes-rails is a web server wrapper for and interface to your local iTunes application.
WARNING: iTunesRails overwrite the (hopefully little-used) "comment" field of your iTunes tracks to record the last person who queued that track. So if you have any comments on tracks you want to preserve, please do not queue those tracks on iTunesRails, or don't use iTunesRails.
Once the code is checked out from the code repository, type
cd itunes-rails
and then
mongrel_rails start
This should start itunes-rails. Open a web browser to the URL
You should see the itunes-rails web interface.
If the Terminal complains that you need a newer version of Ruby on Rails, type
sudo gem install rails -y
and enter your OS X user account password (assuming you're an administrator on this Mac). That should bring you up to date. Then repeat the instructions starting above at "mongrel_rails start".
To let other people on your local network access the same interface, make sure you turn on Web Sharing in the Sharing System Preferences panel. People should be able to hit itunes-rails using your computer's website address as indicated by the Sharing Preferences panel, with ":3000" appended to it.
iTunesRails is still evolving. To get the latest features and bugfixes, cd into your itunes-rails directory and type
svn up
This should update the code. Then stop the mongrel_rails process (with Control-C) if you haven't already and restart it with "mongrel_rails start".
To let other people easily drop in audio files and have them automatically added to the iTunes library running behind iTunesRails, you can set up a shared folder with the appropriate Automator folder actions. A more detailed guide on this is forthcoming.
Feel free to report any problems or feature suggestions via the Issues tab above.
Enjoy music, enjoy life.