Simple, easy, clean, and beautiful.

ConvertKit offers a simple, easy to use interface for building sign up forms and their website is chock full of advice on getting people to sign up and how to best utilize it. Tons of easy to use pre-built forms and layouts too. I would join them just to get their update emails that encourage smart marketing practices and show you how others are utilizing their software. It works seamlessly with my WordPress site and looks beautiful. I took the free trial and signed up immediately after that!