Everyone and their sister has a howto for getting LDAP running on Linux. Unfortunately, most of them are either outdated or just plain crap (with a nod to the Linux Outlaws). Fortunately, just last week, AlbanianWizard has posted a script and a mini-howto for getting LDAP running on Ubuntu 10.4.
I'll post my notes in the wiki shortly. The one thing that I'd add to AW's work concerns the installation of phpLDAPAdmin. He left out that, if you change the container, you'll need to edit /etc/phpldapadmin/config.php. Basically, look for the uncommented lines which contain "dc=example,dc=com" and change the values to whatever you used in building your directory. If you don't, phpLDAPAdmin will always try to access example.com and will error out, even if you change the domain on the login screen.