Aaron Axelsen

LDAP authentication is configured on a site-wide (as opposed to per-blog) level, so only Network Admin accounts have access to the configuration to LDAP connection information.
Please make sure you have PHP compiled with LDAP support. This will show up as an LDAP section in your phpinfo() if it is correct.
Remember – all the code for the plugin was contributed by volunteers, and you can show your gratitude by giving back to the community!
<h3>How It Works</h3>
When enabled, this plugin can automatically create WordPress user accounts and blogs for LDAP-authenticated users. Assuming user credentials authenticate against the LDAP server, creating local accounts and blogs follows this 
algorithm:
Create a new WPMU User, with LDAP username and a randomly generated password. 
Some user information, such as first and last name, is extracted from the 
 information returned from the LDAP server. 
Actions for user creation and activation are triggered. 
The user’s domain / URL are created depending on plugin configuration (i.e., 
 VHost vs SubDir). 
If the option is set, a blog is created, with path and name based on the LDAP 
 username and the blog is activated with the user being Administrator, and 
 appropriate actions are triggered.
It should be noted that even though a random password is created for a user (for WPMU accounts), it is never displayed to the user. This is intentional so that there is no confusion as to which password should be used; it will always be using LDAP credentials. As a result, though, if ever LDAP is disabled or if the server is unavailable, users created with LDAP authentication will be unable to log in unless their passwords are reset.

WPMU Ldap Authentication

A plugin to override the core WordPress authentication method in order to use a LDAP server for authentication.  Currently only supported on MultiSite …

qoelhex

Just LDAP auth, no other features. A minimalistic approach to auth when you need just auth and no other hassles with it.

WPMU Ldap Authentication vs HELLDAP