I am using XForms to create a "contact us" form on a site. One of the fields is a "email" field, and I would like to send a confirmation with some additional information to that email when the form is submitted. Is that something that can be done?
Yep. XForms raises a number of events which can be tied in to, allowing you to perform custom actions such as sending an email to the person submitting the form. As I recall, there's an example in alloy in global.asax.cs.
To send an email after the form's been successfully posted, you can tie in to the AfterSubmitPostedData event.
If you have the choice you are better off using the new Episerver Forms module: http://world.episerver.com/add-ons/episerver-forms/
The ability to send a confirmation to a person's email is out the box with the new forms module.