You can use a contact form in an overlay, but it is not as easy as directing an external web page to an overlay like in the tuturial in this website. What I have found is that you have to validate the form using ajax and php in order to make things work.
There are online premade overlay contact forms that are pretty nice, but none of them work for what I'm trying to accomplish so far. Contact-Pop and simplemodal-contact-form are a couple you can put in your search engine.
Contact-pop is easy to use and it works off your contact page link. So, whenever someone clicks a link that would normaly go to your contact page it opens up the overlay contact form. That way if they don't have javascript enabled they will still be directed to a contact page.
I'm making a website for a school and I have a page with all the teachers and there contact. I want to make it so that if you want to contact a teacher you can open up an overlay for that teacher and contact the teacher without having to leave the curent page.
If you find a way to do that let me know. As far as I know it hasn't been done or realeased as a tutorial yet.