Ask HN: Forms as a service

I created a tiny static site and I want to add a contact form and signup button. What service would you recommend to quickly add these forms without a single line of server side code?

Edit: Sorry if this is a silly question; I'm a backend developer and my instinct is to throw Django or Rails at this. That can't be the simplest solution.

Edit2: I'm really just looking for an API. I have nice CSS forms already and I want to save the data somewhere.