ClearCase can be used as your configuration manger like source control, and
you can use clearquest as your change management (activity, and defect
tracking). You can integrate both of them as UCM(Unified Change Management)
and manage all of your changes and track them in managed environment.
Fortunately, there is a plug-in for MS Project to integrate your CleatQuest
with MS Project.

1. ClearCase Server is not in the standard Rational Suite package and you have to get a license separately. If you found it expensive there is another one called ClearCase LT a little bit less-expensive

2. The relation  now:

ClearQuest is a trouble ticketing application. Once a problem is found, it will be recorded in ClearQuest (CQ). An engineer will then take responsibility of resolving that recorded fault.

ClearCase (CC) is then used to take a snap-shop of the code and once the code is fixed, you check in the code back in and then set the opened ticket in CQ to a resolved state. CQ ticket can not be changed to resolved unless you modify the code or close the opened snap-shot of the code.

CC is the tool for source code version controlling a CVS. This is a much more advanced tool in comparison to Microsoft SourceSafe

CC is the one that you should use to large teams and it allows multiple engineers to work  on a single file of the same version at the same time.

It can also be used for documents too, but it doesn't show the difference of the documents of the same version and that is up to the document editor. Although it will be merged with Microsoft tools very good.

Rational ClearCase is a Version Controlling System - SCM ( like other CVSNT, VSS etc.,)
Rational ClearQuest is a Bug Tracking System.

Pls go thru www.theserverside.com/.../thread.tss for Rational Suite ..full details...