Custom CSV Export Plugin by mburtis is a WordPress plugin that allows you to export the values of custom fields into a CSV file. You can choose a post type (including defaults posts or pages) as well as a list of custom field keys you wish to export. The plugin pulls the values for those fields from all instances of your chosen custom post type and provides a link to export them as a CSV file.
Download: http://wordpress.org/plugins/custom-csv-exporter/