You can use the AD schema snapin from the mmc.exe.
You might need to register Schmmgmt.dll:
- Click Start, and then click Run.
- Type regsvr32 schmmgmt.dll in the Open box, and then click OK.
- Click OK when you receive the message that the operation succeeded.
Here is the user id attribute OID: 0.9.2342.19200300.100.1.1
There might be some scripts out there to retrieve what you want but with the MMC you should be fine.