The Form Assembly
This site is incredible. If you are interested in client-side tools to improve your forms check this now.
One of the online tool I already used a lot is the Form builder. You can create any HTML form, including some advanced stylesheets.
The Form Builder
The Form Builder is a tool for creating standard compliant web forms. It integrates the wForms extension and relies on a set of technologies like XML, XMLHttpRequest, XSLT and DOM (a.k.a Ajax) to provide a seamless single-screen experience.