If you are searching for a plugin to create a complex forms in your WordPress site, your best option is the cForms. It is free and GPL licensed and has a wonderful UI.
The best feature of the cForms is the multi page forms and it is very easy to implement too. Most of the free form plugins doesn’t provide this feature. Here are some of the other great features.
- Ajax supported form submission including graceful fall-back.
- Multiple forms on single page.
- Drag and drop form management
- Submission limits along with start and end dates.
- Database based tracking of submitted data.
- Clean separation of CSS styling and form code
- Backup & Restore
For more information : http://www.deliciousdays.com/cforms-plugin/