[Zope] Product for user registration?

Hi, Anybody recommend a product or system that for users to register themselves in a Zope site? Basically, I want to have the functionality of the Plone registration process, but I don't need the whole Plone system. I'm guessing that I'm going about this the right way; I want to do light-weight user-membership types of things - customized preferences, saved searches, opt-in mailing lists, etc. The Zope user model looks perfectly adequate to build on to make these - no reason to use Plone, and then have to dismantle and not use most of it. And so, I'm wondering if there's a stand-alone package for users to register and eventually cause an entry in a user folder to be created. Thanks, Robb