Help finding reusable forms (I think)

Hi there, first post from me. I’ll try to explain what we’re looking for.

We’re working on this WP-based page, where we would like people to be able to use a form like this one: http://www.electricfarm.dk …or with the same features.
The one on the page is not working, but if it were, it would enable people to send information about whether or not they are attending, how many people will be attending, their names, age and so on.

So a reusable form (plugin), that can be added to any post, and the info gets sent to the admin via email. The form must be editable with out having to work in the actual code.

Hope it makes sense.

Cheers
Odgaard