While Google has long dominated PC search, leadership in the emerging mobile search space is up for grabs as vendors experiment to develop useful layout designs and search algorithms.

For example, because mobile devices have small screens and slow connections, search engines need to offer fewer but more-targeted results and collate results like local business listings, maps, photos and news.

In March, Google released a new mobile search engine accessible from a Web browser and customized with preselected weather, news, stocks and movies data, for a specific locale.

Google also announced a service that lets users text a flight number via SMS (short-message service) for flights departing or arriving in the United States and get information on the flight’s status.

The same day Google released its new mobile search engine, Yahoo announced a new mobile advertising network, plus opened up its mobile OneSearch offering to any phone that can access the Internet. Yahoo OneSearch previously was available as part of Yahoo Go for Mobile, compatible only with certain handsets.

Rather than displaying lists of links as search results, OneSearch pulls up a range of results, including news headlines, images (such as Flickr photos), business listings and reviews.

As for rivals, handset makers like Nokia often include their own search mechanisms. For its part, Microsoft announced in March that it will purchase Tellme Networks. Tellme enables voice-based directory assistance and mobile search: People use it to find directions or movie times, for example; companies use it to help customers do jobs like track packages.

Along similar lines, Google announced in April an experimental speech-recognition-based program, Google Voice Local Search, that lets you search for local business information. Check it out at 800 GOOG-411 (800 466-4411).