I am trying to set up a committee registration form where the registrant also adds contact information for three other people (more contacts being added as the number of people grows in that group). How can I do this with Civicrm? Until now I was adding custom datafields for the other 3 contacts, then I realized that more people will be added later, so I can't be creating a custom datafield per person. If I create a new profile, how can I embed it in the initial registration form? Is there a way to add fields dynamically to a form (so that the registrant can add more than 3 people during registration)?
There's no way to dynamically add fields without custom code to a profile - and that code sounds onerous. There's a better way, though: I'd recommend creating a CiviEvent and enabling "register multiple participants" from there.
You've tagged this "Wordpress", which rules out using Drupal Webform with CiviCRM integration. That's another alternative for anyone else with a similar issue using Drupal.
There's now a new option, the Profile Conditional extension. This extension requires some tech know-how to configure, but you need not be a programmer.