OpenDS will turn out to be a very popular project.
The team has been taking a soft-launch approach but they actually are already
in pretty good shape -
check the OpenDS tag for some earlier news.
Trey recently wrote a blog entry contrasting
LDAP with RMDBS.
In part it boils down to whether your application data is better modeled by
title="Hierarchical model">Trees or
Check out Trey's blog.
You may want to also check the
LDAP page at Wikipedia,
and the latest standard spec,