YouTube will already be familiar to many as a place to find ads. Below are some other sources.
Below are links to the websites of a few of the trade publications for the field of advertising. How much content will be available free on these sites will vary. For a complete list of all the journals and magazines at Marquette's Libraries, print or online, click here.
Here are links to some of the big name research companies in the field. As a general rule, there is little or no free content on these sites.
In addition to the link to the Ad Council below, a Google search on the phrase "public service announcements" will bring up links to PSA's available on the websites of many non-profit organizations.