List of OS used in Mobiles...

Android

Android is the name of the Linux based operating system that is backed by Google and the other members of the Open Handset Alliance. Because of Android’s open source nature, Android based smartphones should be cheaper to produce than those that use operating systems.
And there are various mobile which used this operating system And some top smartphone which use the same platform like Sony xperia , HTC Desite , LG optimus etc

Apple iOS

Apple released the iOS operating system which is used in iPhone was launched on 29^th June 2007 when the iPhone was developed. Since then there were many updates of iOS and the latest one is the iOS 6. Apple iOS is unique and is only for Apple iPhone & iPad and no other manufacturer can use this operating system platform.
Some of the latest Windows Phones are iPhone, iPhone 2G, iPhone 3G,  iPhone 4, iPhone 4S, iPad, iPad2, iPad3.

Blackberry OS

Blackberry OS developed by Research In Motion (RIM) and was released in 1999. BlackBerry Os is running on every smartphone which is designed by RIM and the strange part is that Blackberry OS is totally dissimilar from other operating systems.
Some of the latest Phones are Blackberry Bold, Blackberry Curve, Blackberry Torch.

Windows OS

Windows OS is widely known OS as this is used in our desktop and Laptop computers but not everyone knows about Windows OS in detail because it is used in computers all over the world, but Windows OS running on Computer and mobile phone are totally different things.
Some of the latest Windows Phones are Nokia Lumia 800, Nokia Lumia 900, Samsung Focus, HTC Titan 2.

Symbian

Symbian OS is formally the possessions of Nokia. If any company wants to work on this OS will have to take consent from Nokia. Nokia was a leader in the mobile market, so after Java symbian was ultimately widely used mobile phone some time ago when iOS and Android were not in the picture.
Some of the latest Phones are which using above operating system is Nokia E6, Nokia 808 , Nokia 701,  Nokia C 6.

BADA

Exactly like Nokia Samsung also has own operating system named as BADA. It was intended for high and Low end smartphones. Bada is a user friendly, effective & efficient operating system, Strange thing is that Samsung do not use Bada OS on a big scale for its handsets instead Samsung too uses Android on a immense scale for some unidentified reasons.
Some of the latest Phones are which using above operating system is Samsung Wave, Samsung Wave2, Samsung Wave3.

Palm OS (Garnet OS)

Palm OS was created by Palm Inc in the year 1996 in particular for PDAs (Personal Digital Assistance) and is used my many huge companies like Lenovo and IBM. Palm OS was originally intended to work on touchscreen Graphic User Interface. It was updated few years later and was able to work with and sustain smartphones. Unluckily Palm OS was not able to do well in the market & due to that it is not being used in any of the latest top devices.

Open WebOS

Open WebOS or Hp WebOS or just WebOS which was originally created and promoted by Palm Inc in the year 2009 but years later this OS was acquired by Hewlett Packard. At that time this OS was used in several Smartphones & tablets.

Maemo

Nokia & Maemo both companies came together to create an operating system for smartphones & internet tablets, named as Maemo. Similar to other devices the user interface of Maemo also contains a menu which provides user an access from which the user can go to any location.

MeeGo

MeeGo was fundamentally called as a mobile platform but it was in reality intended to run several electronic devices which includes handhelds, in car devices,
television sets & in even net books. All the devices on which MeeGo OS can operate although have the similar core but difference lies entirely in the interface according to the device.
There are more Mobile Operating systems and if rumors are to be believed then we we’ll be lucky enough to see Firefox Mobile. Android has emerged as an undisputed winner, nevertheless, if we compare in terms of profits & expansion, Apple iOS has emerged as the biggest Tech company which leaves Google Android far behind.