Can Webforms include the URL they were submitted from in their emails?
You can achieve this by using the %server token as the value of the hidden field. To be more precise http://%server[SERVER_NAME]%server[REQUEST_URI] should get you the full url (path alias is also preserved). For a complete list of options that can be used with the %server token check out the manual.

UPDATE:

The %server token only works for authenticated users since Webform version 2.8 due to potential security/privacy issues with some values. Since you only need the url in e-mails a better solution should actually be to put a appropriately themed version of &lt;?php print url($_GET['q'], array('absolute' =&gt; TRUE)); ?&gt; inside your copy of webform-mail.tpl.php file (or webform-mail-[node id here].tpl.php).