Downloads: verifyemail.backup. Requires the email plugin to be enabled.
Here is a backup file you can extract to setup an email verification system. Use main.enroll instead of your built in action.register form. Pages created include:
Make sure you have the email plugin enabled, and authorization given for main.enroll.account to send emails. You also need to allow guests to write to temp.activate pages.
You will also need to edit some of the pages to your needs, such as entering your return email addresses, etc. So look them over carefully, and use them as a framework for whatever changes you wish to make.
Suggestion: you can easily insert a profile page between the verify and start page, if you wish to collect additional member information from your new users.
If you have any problems, let me know and I'll try to make sure I haven't omitted any needed pages or neglected to mention some setting or other.