This has been quite a week for news about mobile phones and smartphones of all stripes. Apple's (NASDAQ:AAPL) finally made the iPhone a reality. Palm (NASDAQ:PALM) launched its long-awaited Treo 750. And now Yahoo! (NASDAQ:YHOO) and Google (NASDAQ:GOOG) have announced new mobile-phone initiatives as well.

A day after Steve Jobs announced that both companies' services will be available on the iPhone, Yahoo! and Google have announced that their services will also be on hand for Samsung mobile phones. But Yahoo! may well have the upper hand.

Rumors have abounded in the past year as to how Google might revolutionize cell phones -- just last month, speculation arose that it was in talks with British phone carrier Orange for a Google-branded phone -- but there's not too much earth-shattering about Google's announcement that Samsung users will be able to access its search, email, and map products.

Yahoo!, on the other hand, seems to be taking a very aggressive stance, given that it's packing some mobile-centric features for mobile phones, albeit under what one might consider a rather unfortunate banner -- Yahoo! Go 2.0. Although still in beta, it will include widgets that allow users to quickly find things they need: email, weather, sports scores, local information and maps, and photo sharing, for example. This service, called oneSearch, seems very significant, because it delivers search results that are more likely to match what cell-phone-toting folks are looking for on the go, as opposed to those who are doing more leisurely, research-oriented searches on their home computers.

Furthermore, Yahoo! also said it has agreements to deliver its services to Nokia's (NYSE:NOK) and Motorola's (NYSE:MOT) handsets and Research In Motion's (NASDAQ:RIMM) BlackBerry. In addition, many consumers can download Yahoo! Go 2.0 for their own phones.

At stake, of course, is the growing market as people continue to use more features on their mobiles. The related advertising opportunities are there, too -- the numbers that many news services are throwing about state expectations for $1.5 billion in mobile advertising this year, and at least double that by 2010.

If Yahoo! Go 2.0 proves as useful as it sounds, doesn't it seem that maybe Yahoo! has one-upped Google for the first time in ages? It remains to be seen how the battle pans out, but with so many people focusing on Yahoo!'s weaknesses here lately, investors should pay close attention to the company's aggressive moves into this high-growth arena.

Yahoo! and Palm are Motley Fool Stock Advisor recommendations. To find out what other companies David and Tom Gardner have recommended to subscribers, click here for a 30-day free trial.

Alyce Lomax does not own shares of any of the companies mentioned.