How do I pass variables into short-code enabled Post Snippets in WordPress 3.0?

The Variables in Post Snippets (WordPress Plugin) is a comma seperated value. When you use the snippet-insert button in the post/page editor, you can set those.

An example of this is given on the homepage of the plugin, there is even a screenshot demonstrating that. Please read the documentation first.

Those Post Snippet Variables are totally unrelated to PHP variables. I think that’s just the thing you missed. You were looking in the wrong direction.