McKinsey has looked at 60 US Fortune 500 or similarly sized companies and the progress that these companies were making in advancing their women.
They measured the companies on 4 metrics:
A startng position that reflects the talent
More women at the top
Better odds of promotion
Women in the line
A summary of the report findings and the actual report itself can be found at:
http://www.mckinsey.com/client_service/organization/latest_thinking/women_at_work