Display summary of entered field values and permit user to cancel submission
There is a feature request for a "summary" component for Webform in the Webform module issue queue here: http://drupal.org/node/435232, but there isn't any movement yet on actually making a built-in summary component in the core project.

In that issue, dealancer notes that he has already added his code to the http://drupal.org/project/webform_bonus project, which allows you to add a summary component directly to your form in the same way you would add a textfield or any other component type. Install that module and add a summary field to your form, selecting which fields you would like to include in the summary. If you would like it on its own page, make sure to add a pagebreak component first.