The Google Android OS was announced around November 2007 and can be termed as a potential threat to Microsoft's Windows Mobile OS. Many brands are in favor and supporting this OS introduced by Google. Along with "open handset alliance" which brings together 30 technology and mobile companies, Google developed the Android, the first open and free mobile platform.
The main difference between other OS and Android is that its "open source", means that other developers and manufacturers have the choice of writing their own add-on applications as as the code is being made freely available. This brings in flexibility and helps in betterment of the application. Google has announced a prize money of $10 milliion for the best third party software developers and the applications developed by them on Android.
A Google Android Demo can be viewed on YouTube on the link http://www.youtube.com/watch?v=p_75Tq3oSNw