One of the favorite products of many Tivoli security professionals is Tivoli Directory Integrator. I have to say it's one of the coolest software products I've ever worked with. IBM currently ships it with a number of other products including one of my past passions Lotus Domino.
Anyhow if you are new to Tivoli there's a great wiki here: http://www.tdi-users.org/twiki/bin/view/Integrator/WebHome
Also finally I'm not the only one blogging about Tivoli thanks to Eddie's new ITDI blog. At least now there's someone who really knows what they're blogging about: