WARC, the "World Advertising Research Congress" (I believe) is a really huge marketing repository of knowledge with thousands of cases, category reports, analyzable by country, region, marketing speciality, year.
Although it is subscription only, you can sign up for a free trail. The trail is time limited so sign-up, when you have some time to explore it.
It really is terrific. A must have for big marketers and agencies, and am including digital, media and research companies in that too.