So far [as of Dec 8th] 39 registered volunteers have published research on 40 Fortune 500 companies. 42 companies have been identified as having at least one public-facing corporate blog. Volunteers have either researched or signed up to research 95 companies.
All of the blogs (and reviews of those blogs) are listed here. It would appear that the project was initiated by Easton Ellsworth, who writes for Business Blog Wire and is apparently (!!) only 25 years old.
If you would like to join in this noble effort, you can sign up here.