I’ve been receiving more requests for corporate research lately and I ran across two useful sites that are used in the activist community but could also be used for donor research
Endgame, the site of Seattle area activist researcher George Draffan, has a terrific set of links as well as some corporate profiles
is a collaborative wiki created by activist nonprofit organizations as well as individual contributors. This site has great information and corporate profiles.
Both these sites are well researched and have an activist bent, making them particularly useful when performing due diligence before accepting gifts or making grant requests.