Umbraco Forms Documentation
Documents how to work with Umbraco Forms (HQ's official Forms Builder) from both an editor and a developer standpoint.
You can purchase Forms from Umbraco Apps.
Extending Umbraco with the Forms section and keeping it up to date.
Interact with the interface and build Forms in a couple of clicks.
Covers retrieving data from Forms, extending the system by hooking into the provider model, and the available events and workflows you can use to extend or integrate Umbraco Forms.