All tutorials I have found say to add your shortcodes to functions.php in your theme. I would like to break that away from my theme and put that in a plugin so I can share these shortcodes between my network of blogs. Is there a reference or tutorial on creating these shortcodes in a plugin?
Basically you just take your code out of
But there will be no difference in how code actually works.
See Writing a Plugin for a starting point.
Basically, you just prepend your functions with a plugin header.
As a really simple example, I just put my shortcode plugin to GitHub: http://github.com/toscho/WordPress-Shortcodes
It is missing I18n – as usual :) – but it should give you some hints.