NetWrix

NetWrix Group Policy Change Reporter - for Group Policy change auditing. They offer a free and paid version of their product.

SDM Software

SDM Software, provides a whole suite of tools for better managing Group Policy. These include:

• GPO Compare: Powerful tool for reporting on inconsistencies and differences between two GPOs, including both live and GPO backups. Now supports Win7 and all new settings!
• GPO Exporter: Provides a quick and powerful way to document all your GPO settings, and includes the ability to search, sort, export to CSV, Excel or PDF.
• GPexpert(r) Group Policy Automation Engine: The only product on the market that lets you automate changes and audits of Group Policy Settings, using PowerShell or .Net. 
• GPExpert(r) Troubleshooting Pak: Four products that help you track down and solve Group Policy problems. 
• Group Policy Health Cmdlet: Provides a free PowerShell-based command-line tool for retrieving Group Policy status across multiple machines in your AD environment
•  Group Policy & Active Directory Freeware: A variety of free tools for managing Group Policy and Active Directory

Quest Software

Quest Software is a familar name in the AD management space, have Group Policy change control products and Quest has some Group Policy extension products as well.

Centrify extends Group Policy to the non-Windows environments

Centrify extends Group Policy to the non-Windows environments with their DirectControl. Most interestingly, they have DirectControl Group Policy for the MacOS! Pretty cool

NetPro

NetPro is another familar name in the AD management space, have Group Policy change control products.

NetIQ GP Extensions and GPO Change Tracking

Another vendor for GP Extensions, GPO change tracking and version control is NetIQ, who acquired their products from Full Armor--one of the early vendors in the Group policy space. Full Armor has a set of GP products as well.

Special Operations Software Group Policy Products

Check out the GP products from the Swedish company Special Operations Software. They have a couple of interesting GP-related products, including SpecOpsDeploy, which extends what you can do with GP-based software installation, and SpecOps Password Policy, which lets you set different password policies within a single AD domain.

Free GPO-based utility for managing power settings

This is a pretty cool. Its a free GPO-based utility for managing power settings on a PC: http://www.energystar.gov/index.cfm?c=power_mgt.pr_pm_ez_gpo