Zapof is a truly amazing form builder. It has a huge library of field types, and even allows embedded calculations, which allow you to create forms that calculate (e.g. for sales tax), change fields according to previous answers, and accept signatures. There's a huge template library to get you started, and creating a new form from scratch is pretty easy.

I've found the support responsiveness to be excellent. I emailed with a problem and received a response within the hour, solving my problem.

I almost feel like calling Zapof a form building doesn't do it justice. My sense is that it may well prove to be a major interaction tool for anyone who is managing a community, running events, or collecting data via the web.