Confirming its long-rumored foray into the mobile market, Google today announced an ambitious alliance with a number of handset makers, wireless carriers and other technology companies to create potentially cheaper mobile phones based on an open source platform called “Android”.

Google will not be making the phones and doesn’t plan to stamp its brand on the devices either. Instead, mobile manufacturers Samsung, HTC, Motorola and LG have all agreed to take their proprietary closed products and ‘open source’ them using Google’s platform, which will be provided to them free of charge. A development tool kit for working on the new platform will be released next week, allowing developers to create new applications and other software improvements that could spawn new uses for smart phones. However, phones powered by Google’s technology will not appear before the second half of 2008 through T-Mobile and Sprint.

The agreement could boost Google’s advertising revenue from mobile phones – a market that is expected to reach $11.4 billion worldwide by 2011. For mobile carriers, the deal could also drive sales of online services and give them an edge over rival AT&T, the exclusive U.S. carrier for Apple’s iPhone.