This is a little sketchy at the moment, but will be extended in the future :-).
The open ldap folks produce a nice extensible stand-alone
directory, along with some general ldap information:
A list of ldap resources is available from the folks at King Mountain software:
king mountain ldap links
For the dedicated, a read through the base ldap faqs is always rewarding! You can get the definitive versions from the ietf: RFC List - but I'm rather fond of the html hyperlink enabled versions maintained by faqs.org.
Base ldap rfc: rfc2251
Attribute Syntaxes: rfc2252
UTF-8 Distinguished Names: rfc2253
Search Filters: rfc2254
Ldap URLs: rfc2255
X500 User Schema: rfc2256
LDIF file format: rfc2849