The following sites provide archival access to well-known print and audio-visual ads. We also have quite a few collections of television commercials on DVD, as well as books on Advertising that often feature images of print advertisements. Try the search terms "television advertising" or "advertising" in Omni.
Some companies or organizations will archive advertisements on their website. You may also be able to locate television commercials on the company's official Youtube channel.
Many mass media and advertising channels (such as newspapers, magazines, radio stations, etc.) produce media kits or advertising rate cards, which contain information about the audience (circulation figures for print-based products) and online or mobile audience demographics (age, gender, income) for online/digital media. Advertising rate cards may provide current prices for placing advertisements on sites, in print, or across media channels.
To locate the media kits and rate cards through Google: search for the name of the source and the words "media kit" in Google. For example:
The following sources provide additional insight in specific media channels. Some reports are updated annually, while others may have been "one-time only" studies.