Advertising ain't what it used to be. In the past few decades, companies wanting public awareness of their brands would plunk down a few million dollars for TV advertising campaigns, or just go for the gold with an expensive Super Bowl spot. TV was King, and the biggest event of the year was where you showed off your best side.

But these days, there is unrest among the natives. The Internet has opened up new avenues between corporations and consumers, and the recent rise of user-submitted video services like MySpace, YouTube, and Google (NASDAQ:GOOG) Video is changing the rules of the game. Popular ad spots from the television world can often be found online within hours of the original airing. Anybody with a webcam or camera phone can make a heartfelt or spoofy commercial of their own in just minutes -- and make it available to the world in a few clicks.

The power of community is enormous. Make people feel like they belong, and they will like your product better. That's why some respected corporations are turning to grassroots efforts to power their brands these days.

We're talking about traditional big-budget advertisers like Nike's (NYSE:NKE) Converse brand, Bayer's (NYSE:BAY) Alka-Seltzer, and General Motors' (NYSE:GM) Chevrolet. All of these companies are looking for user submissions to insert into their TV advertising campaigns. In some cases, users are even competing for that gold-plated Super Bowl airtime.

Chevy, for instance, took submissions from hundreds of college students through a targeted contest, picked a winner, and is now producing the clip with professional actors and equipment. Pepsi's (NYSE:PEP) Doritos subsidiary has chosen to run a hands-off contest, with submissions posted on Yahoo! (NASDAQ:YHOO) Video and other users voting for the winner. There is no reshooting or professional editing involved. And the National Football League itself invited fans to pitch ideas for a professionally produced spot that will run during the Big Show.

Even companies that not too long ago seemed averse to fan-made clips are coming around to the idea. Remember that nutty Diet Coke and Mentos geyser fad, and Coke's (NYSE:KO) cold shoulder to that instant community? Now Coke is an official sponsor of the whole thing, through a series of sponsored clips on Google Video.

Grassroots marketing seems to be an idea whose time has come. This February, you'll see several marketing ideas from fans just like yourself in those timeout and side change breaks, while pouring a Diet Coke and refilling the Doritos bowl. The response to those ads will tell us -- and Pepsi and Chevrolet -- whether or not the strategy is worthwhile. Chances are, it will work. Listening to your customers almost always does.

Further Foolishness:

Coca-Cola is a Motley Fool Inside Value recommendation, and Yahoo! Is a Stock Advisor pick. Check out either service -- or both -- with a free 30-day trial.

Fool contributor Anders Bylund is a Coke shareholder, but holds no other position in any of the companies discussed here. You can check out Anders' holdings if you like, and Foolish disclosure is always Super Bowl-worthy.