Recently I needed to filter the return of get-psdrive to return all of my local hard drives.  I didn't want to accidentally start operating on floppies, CDROM's and more importantly, network drives.  There are a couple of ways to do this but I found the most straight forward is to combine the WMI data with get-psdrive. 

E:\temp> get-wmiobject win32_volume | ? { $_.DriveType -eq 3 } | % { get-psdrive
$_.DriveLetter[0] }

Name       Provider      Root                                   CurrentLocation
----       --------      ----                                   ---------------
C          FileSystem    C:\                                 ...nfig\PowerShell
E          FileSystem    E:\                                               temp

DriveType is a property of the Win32_Volume structure which enumerates the type of drive.  The value 3 stands for Local Disk.  Below is the full list of values.

0 - Unknown
1 - No Root Directory
2 - Removable Disk
3 - Local Disk
4 - Network Drive
5 - Compact Disk
6 - RAM Disk