First stop would be to check out the recently published TechNet Article Recommended Updates for Group Policy in Windows Client and Server Products

Then take a look at this list of recent  old Group Policy Hotfixes released from Microsoft.

Note: This page is no longer updated. Please follow me on twitter if you want notification of new Group Policy related hotfixes.

• Group Policy preferences client-side extension hotfix rollup for Windows Vista http://support.microsoft.com/?kbid=977983
• Client-Side Extension Hotfix Rollup http://support.microsoft.com/default.aspx/kb/974266
• User password is set to NULL when you use Group Policy Preferences to create a user account http://support.microsoft.com/?kbid=971357
• After you apply a GPO to redirect a folder to a new network share, the redirected folder is empty on client computers that are running Windows Vista or Windows Server 2008 http://support.microsoft.com/?kbid=977611
• Some templates are missing in Administrative Templates item after you enable a filter option by using the Group Policy Management Editor window on a computer that is running Windows Server 2008 http://support.microsoft.com/?kbid=949360
• LDAP filters in the Group Policy preference settings do not take effect on a computer that is running Windows Server 2008 R2 or Windows 7 http://support.microsoft.com/?kbid=976398
• FIX: You cannot apply Group Policy settings on a computer that is running Windows 7 or Windows Server 2008 R2 when security group filters are used in Group Policy preference settings http://support.microsoft.com/?kbid=976399
• Error message when a Group Policy client-side extension cannot log RSOP Data:”0x80041002″ http://support.microsoft.com/?kbid=977755
• Error message on a domain controller that is running Windows Server 2008: “The client-side extension could not remove user policy settings for ‘Domain Name {GUID}’ because it failed with error code ‘0x8007000d The data is invalid.'” http://support.microsoft.com/?kbid=977564
• The “Run only allowed Windows applications” Group Policy setting displays no entries on a computer that is running Windows Vista, Windows Server 2008, or Windows 7 http://support.microsoft.com/?kbid=976922
• The “Desktop Wallpaper” Group Policy setting is not applied in Windows 7 or in Windows Server 2008 R2  http://support.microsoft.com/kb/977944
• The “Configure new tab page default behavior” Group Policy setting does not work on a computer that is running Windows 7 or Windows Server 2008 R2 and that has Internet Explorer 8 installed http://support.microsoft.com/?kbid=980959
• The Group Policy preference settings for the “Terminal Session” item-level targeting item are not applied in Windows 7 or in Windows Server 2008 R2. http://support.microsoft.com/kb/981054
• You can still unpin a program from the taskbar unexpectedly when you enable the “Do not allow pinning programs to the Taskbar” Group Policy on a computer that is running Windows 7 or Windows Server 2008 R2. http://support.microsoft.com/kb/981177
• You cannot create a software installation Group Policy setting on a read-only domain controller in Windows Server 2008 R2. http://support.microsoft.com/kb/981265
• Error message occurs when you use GPMC to view a software restriction Group Policy setting in Windows 7 and in Windows Server 2008 R2: “An error has occurred while collecting data for Software Restriction Policies”. http://support.microsoft.com/kb/981750

If you want to keep track of all new Group Policy (and Active Directory) hotfixes yourself then check out the Microsoft AD team blog at  Ask the Directory Services Team