Simple Sign-On does have significant integration with WSS, we provide
two types of integration. the first is a "generic" secure forms based
authentication subsystem that allows individuals to login to and to
manage thier AD/Local account via a web part. This allows you to have
an anonymous site and place a user/password web part on any anonymous
page and let the user  logon when necessary. If they try to acccess a
protected resource they are redirected to a logon page (also under
your control). The system works accross server farms and supports any
server that requres an authenticated user (e.g. Exchange, Class
Server, SNA Server, etc.). This product  is called Simple Sign-On,
Enhanced authentication. This product can be customized to support
primary authentication  against an alternate LDAP/SQL system, but still
requires an AD or Local account for SharePoint access.

The other product that supports SharePoint (both SPS and WSS), is the
web version of our identity brokering system. This system allows
users to logon to Sharepoint and to connect to almost any other web
application without having to reauthenticate to that system,
regardless of the method of authentication that they use.