You will need ns_ldap to enable the AOLserver to connect to the LDAP server. Depending on your setup, you will need a patched version that is floating around.
For OpenACS to authenticate against the LDAP server you need to install auth_ldap package.
If you store the password in OpenLDAP as a field, you are fine with the unpatched version of nsldap. If you want OpenLDAP to do the authentication for you (you authenticate using the LDAP authentication mechanism), nsldap with bind support is needed.
Other than that, search on OpenACS for LDAP, there have been some IRC discussions on this topic.