Here are some step-by-step instructions regarding configuring SharePoint to sync with custom AD attributes:

1. Add the custom attribute in Active Directory
   1. This part will have to be your doing; here is some documentation regarding creating custom
      attributes in AD:
      1. http://msdn.microsoft.com/en-us/library/ms675085(VS.85).aspx
      2. http://technet.microsoft.com/en-us/magazine/2008.05.schema.aspx
      3. http://blogs.technet.com/b/isingh/archive/2007/02/18/adding-custom-attributes-in-active-directory.aspx

2. Open up the miisclient.exe (C:\Program Files\Microsoft Office Servers\14.0\Synchronization Service\UIShell\miisclient.exe)

a. This will have to be opened up with the farm admin account

3. Click on "Management Agents" in the ribbon

4. Right-click the Active Directory Management Agent ("MOSS-<name of sync connection>") and click "Refresh Schema"

a. When prompted, enter the credentials for the farm account

5. Once complete, close out of miisclient.exe

6. Go into Central Admin --> Application Management --> Manage Service Applications --> Go into the User Profile Service Application

7. Click on "Manage User Properties"

8. Click on "New Property"

9. Put in the correct information regarding the attribute that was created

10. At the bottom of this page, under the "Source Data Connection" drop down, select the AD synchronization connection you have already configured

11. For the "Attribute" drop down, select the new attribute you have created

12. For the "Direction" drop down, select "Import"

13. Click "OK"

14. Run a full synchronization for the user profile service application and the custom property will get synced (as long as the attribute is set in Active Directory for the desired users)