I have OpenLDAP running on a slackware 10 install.
Using it as the backend for a Samba PDC (just playin around), Addressbook (Thunderbird / Outlook), and genereal /etc cleanup.
You didn't mention WHAT the LDAP is supposed to be used for (login / addressbooks / etc.) but sofar i have not had to use anything that absolutely needed
to have PAM stinking up the place.
if you have to compile OpenLDAP the biggest headache is prolly linking the right db.h in /usr/include (make sure it is from the same minor version as the libs!!!)
Anything that CAN use LDAP will prolly need to be rebuilt with ldap support as it is not done with the standard slackbuilds (Samba / PHP / Apache /etc..)
Everybody loves links so here ya go.
YoLinux: good place as any to start learning about schema and general OpenLDAP config
nss_ldap: Povides the libraries and whatnots to connect to a LDAP server for your normal nsswitch stuff (login / services / etc...)
JXplorer: Spiffy LDAP/x500 browser/editor to make easy changes to the structure and entries in the directory