There also is an international list of CEO bloggers at the New PR Wiki, but you'll have to extract the Fortune 500 companies yourself.
Both wikis demonsttrate the fact that no blog search engine, including Technorati and Google's, is particularly comprehensive or well-organized cross-referenced.
When, oh when, will someone do a blog search engine right?
About BL Ochman
Blogger, social media strategy consultant to Fortune 500 companies, and sought-after corporate speaker B.L. Ochman heads the creative team of whatsnextonline.com. She also publishes the Ethics Crisis blog for SRF Global Translations