I put together a small module for a recent project that extends Webform to include a "roster" form. Basically, you can assign Webform B to be the roster form for Webform A. When a user completes Webform A they're sent a link to complete Webform B. This link can be used an infinite number of times, so the original user could fill out Webform B immediately, or send the link to a dozen others (which is what my needs are). All of the Webform B submissions are tied to the original Webform A's submission, and show up when viewing that original submission.
