Steve Rubel posted a review of Fortune's cover story on Google that includes this interesting quote:

Fortune magazine has a lengthy cover story on the chaotic way Google runs. What's clear from the piece is that Google is desperately working hard to find its next hit because it's really only had one - search. Even Eric Schmidt notes that Google's most die-hard fans can't remember all of their products. Most folks I know use one, Google.com.

Is search Google's only success to date? Absolutely not. Search was Google's first success, and continues to be their primary offering. However, Google Adwords and Google AdSense are clearly big hits as well. In fact, AdWords and AdSense are by far the main sources of income for Google, so discounting their value is a major oversight.

Google wasn't the first company to create a pay per click program. For a while, Goto.com, which became Overture and was later acquired by Yahoo was the dominant player in pay per click search. The day Google launched AdWords it was clear to me and many pay per click marketing colleagues that the game had changed. The more sophisticated matching options gave users more control over when their ads would be shown while at the same time allowing Google to display ads on a larger percentage of searches than Overture's system allowed. Since acquiring Overture, Yahoo has been in catch-up mode with painful delays in upgrades to their now dated pay per click ad service.

In addition to AdWords, Google AdSense is another hit not to be ignored. Google AdSense has become a major revenue source, and in some cases the primary revenue source, for thousands, if not millions of bloggers, news sites, and other online publishers. Figuring out how to serve ads contextually relevant to the content of million and millions of pages is no easy task. Doing so leads to relatively high click through rates, which drives traffic to advertiser's sites while driving ad dollars into publisher's and Google's pockets.

Maps is an interesting one to consider as well. It hasn't become the market leader, currently lagging behind MapQuest and Yahoo if my memory serves me right. However, if you count the thousands of sites using the Google Maps API, I imagine Google's mapping technology is more distributed than people give them credit for at this point. Not a bad position to be in as they start to roll out advertising onto those maps.

Looking ahead, adding additional ad distribution channels to AdWords such as radio and print advertising buys through a single ad buying interface makes like easy for advertisers. Creating new, higher paying, or less costly ad inventory (inventory without a sales team) opportunities for publishers in fields beyond the web is a clear growth strategy for Google based on their experiments with print and their acquisition of radio ad companies.