retlehs/roots — pull request #204 by Covi (2011-12-31 16:27:06+00:00)
Title: 'wp-content' could be another directory.

You can use content_url(), plugins_url(), etc: see http://codex.wordpress.org/Determining_Plugin_and_Content_Directories
You can use too constants WP_CONTENT_URL, WP_PLUGINS etc... or simple, instead get_stylesheet_directory(), use get_stylesheet_directory_uri() to get content structure through theme files.