System Center admins often get asked for disk space reports.
Depending on the discovery settings the data can be more current in SCOM or SCCM.
So you need to decide which datasource you use.
I have created a report for System Center Configuration Manager 2012, which lists Total Disk Space (MB), Total Free Space (MB), Total Used Space (MB), Total Free Space Percent and Total Used Space Percent.
It sorts by Total Free Space Percent and colour codes the output with this rule:
< 20 %: red
< 40 %: orange
You can select any device collection.
The report can be downloaded here.