On these websites (no subscription) you can find examples of commercials.

The Jean-Marie Boursicot Film Library is giving access to its database of over 450 000 advertising commercials. The database available to you presently catalogs several hundreds of advertising commercials digitized in Real Video. You can search by: year, brand, country, theme or product.
Coca Cola
Fifty Years of Coca-Cola Television Advertisements: Highlights from the Motion Picture Archives at the Library of Congress presents a variety of television advertisements, never-broadcast outtakes, and experimental footage reflecting the historical development of television advertising for a major commercial product.
Use 'movie explorer' to navigate through many (Dutch) commercials (Realplayer or Windows Media Player). This website has an English and a Dutch version.
Adwatch archives UK commercials seen in the last 6 months. They are available to view in small format only. The collected commercials will change when they have seen something better to include.
This site deals with different aspects of advertising. There is an online collection with commercials posted by members of the site.
The Commercial Closet
The Commercial Closet is a non-profit education and journalism project that reaches out to ad agencies, corporations and the world-at-large to create change through reflection on its collection. This site will introduce you to over 750 worldwide sexy and surprising television and print ads spanning more than 30 years, that reflect society’s changing view of the gay community, with marketers' best and worst efforts from around the world.
A website from the magazine boards with good quality commercials for different brands. The commercials are submitted (by the agencies). You need Quicktime to see the commercials.
A website (Ducth) with a collection of commercials broadcasted on Dutch televison and some international commercials.
AdForum is a searchable database of advertising agencies and their creative work. You can search the database for commercials and print ads, using criteria such as clients, products and brands.
In this Tahoo club people view and discuss television commercials from around the world. There are commercials for download in the files area and you can see what others have to say about certain commercials.You can download the commercials at:
Ad Council
For 60 years, the Ad Council has been committed to bringing today's most pressing social issues to the attention of the American people. Ad Council has an online collection of campaigns you can see with realplayer. It also features high quality print campaigns.
Search commercials by product, brand, category or event. You can play the ad with Realplayer or with Media Player.
Classis Car Spots
Some classic car commercials from the USA. You need Realplayer to see the commercials.
Feautures some (old) commercials. Best way to find these commercials is to enter 'commercial' in the search string. You need the apple quicktime plugin to see the commercials in a separate window.
Super bowl commercials
Ifilm collected all the commercials from Super Bowl XXXIX. Just click on any Watch Now! link and you'll be asked to select your Media Player Preferences, then you can enjoy all of the ads broadcast during the game. Plus, they've got the ads they banned.