This sounds not only useful to researchers but also quite fun. Netimperative reports that BlinkxTV, a company that seems to be adding content to their multimedia engine almost daily, is offering (free) a searchable archive of more than 5000 "classic" or "vintage" European television commericials. The commercials are all keyword searchable using speech recognition technology (good, but not perfect). The archive of material dates back to 1945.
The material itself comes from deals Blinkx has made with Diesel, visit4info, the Advertising Producers Association (APA), and the Central Office of Information (COI) to the UK government.
Recently, Blinkx announced that it is working with universities and other institutions like the Smithsonian to make lectures and other special presentations available and searchable online.
A bit more in this news release.