An ad campaign is a series of ads, all for the same product or business, which have a unifying theme, cast of characters, or plot. Some ad campaigns come and go and no one really remembers them once they're gone. Then there are the ones that are used for a long time, are extremely effective, or are particularly memorable. Usually, this means that they are working really well.
This is a page for those memorable, notable ad campaigns. (Of course, since Administrivia/ThereIsNoSuchThingAsNotability, you can actually add any ad campaign with a wiki page to this index.) For more examples, take a look at AdvertisingCampaigns.