Q: How can I track CAL usage of Microsoft products in my environment?

A: System Center Configuration Manager (SCCM) 2007 has the ability to track licenses and CALs for Microsoft (and non-Microsoft) software as part of its Asset Intelligence feature. Once you enable Asset Intelligence and it has run for a while to collect the required information, there are several reports that can be run to give information on license use. For example,

These are documented in TechNet, as are limitations.

One of the great features of SCCM Asset Intelligence is the ability to load in a Microsoft Licensing XML file (which your Microsoft rep can generate using an internal Microsoft Licensing site) that automatically populates SCCM with all your Microsoft licenses and CALs, once you import it with the Import Software Licenses action for Asset Intelligence. More information on importing can be found in TechNet.

Another option would be to use the Microsoft Assessment and Planning toolkit, which includes Software Licensing and Asset Management. It will capture server and license usage without an agent and can then generate reports on the CALs that would be needed. More information on the CAL tracking feature can be found on Microsoft's site, along with a detailed Word document on using the licensing assessment features.