Local User Management Made Simple (lumms) is a local user manager for Linux, AIX and Solaris. It allows you to change local user accounts, groups including passwords from one place. This will update on all hosts the local passwd and shadow files.
OrgLDAP is an extensible LDAP user management application supporting groups, *NIX (POSIX, Shadow), Samba and other account types, SSH public keys and sudo roles. It includes a reusable extensible library and a web-based front-end.