Piklist

Piklist is the most powerful framework available for WordPress. Our free plugin allows even basic users to customize everything; easily add custom fields, settings pages, widgets and more, without having to write hundreds of lines of code. Developers will appreciate the clean, easy-to-understand code that will save you hours of developing time, and save your clients thousands of dollars. Additionally, Piklist supports Post-to-Post relationships, multiple user roles and infinite repeater fields out of the box, making it possible to build powerful websites like never before.

Piklist is available for free at WordPress.org.
Learn more about Piklist at piklist.com.