Sample forms & links to good documentation on creating forms using PloneFormGen. PloneFormGen uses the folder metaphor as the form container, and the file metaphor for the fields within a form. In other words, you can add fields, such as e-mail, name, address, etc., to a form in the same way that you can add files (pages, links, files, etc.) to a folder in Plone. The form actions (e-mail submissions and/or save submission to a CSV file) are added to the folder in the same manner, as is the Thank You page that users see after they submit a form.

Event Registration (SAMPLE FORM)
Sample event registration form with date, personal info fields. This form performs two actions upon submit: Sends a notice to a specified e-mail account and saves a copy of the submission to an spreadsheet-ready CSV file.
Great tutorial on PloneFormGen by Groundwire
PloneFormGen is an add-on product for Plone that allows you to create custom web forms easily. You can create forms that email results to someone, or that can store results on your website that you can later download. This tutorial will cover many of the features of PloneFormGen, but will not delve into the more complex topics that require knowledge of computer programming languages. Additional documentation about this product can be found at Plone.Org
Customizing PloneFormGen
This covers some sample customizations you can make to a form to do various things, such as send a copy of the receipt via e-mail to the submitter and customizing the From: address on the e-mails that are sent when the form is submitted.