I am trying to get the path to the themes CSS file from inside a Plugin, anyone know how to do this?
Get the absolute path: get_stylesheet_directory()
Get the URI: get_stylesheet_directory_uri()
Edit: Here's a proof of concept plugin. It will just print out the stylesheet path and uri in the head tag of your site (front end). If these functions are not working in your plugin, there might be some other factor not explained in the OP. Please post your code.