Hello industrialrobotix,
I haven't seen an email template to resend a portal link. You would have to do a customization. You can create an email template with the URL hard-coded on the email or have a button on the customer screen that sends the customer the reminder email. The email templates are located at CRM tab group -> Home -> Email Templates. If you create an emall template, you can use it on an activity by selecting Send an Email? and then selecting the Email Template you created.
Also, you may consider doing a Save & Email on the contact screen. Select a contact in the Edit Customer screen to bring up the Edit Contacts screen. Check Email confirmation when saving? and Save & Email. The confirmation sent has the portal email as well.
As a reminder, the portal URL can be found following the path Customize -> Portals -> Get sign-in page web address...
Greg