ExpressionEngine template that creates a CSV file from FreeForm data.

contact-csv-output.html

"First Name","Email"
{exp:freeform:entries
    form_name="contact"
    orderby="entry_date"
    sort="asc"
    limit="9999"
}"{freeform:field:first_name}","{freeform:field:email}"
{/exp:freeform:entries}

<?php
    header("Content-type: text/csv");
    header("Content-Disposition: attachment; filename=contact-list.csv");
    header("Pragma: no-cache");
    header("Expires: 0");
    exit(0);
?>