Maemo

Maemo is a software platform developed by Nokia for smartphones and Internet Tablets. It is based on the Debian Linux distribution.
The platform comprises the Maemo operating system and the Maemo SDK.
Maemo is mostly based on open source code, and has been developed by Maemo Devices within Nokia in collaboration with many open source projects such as the Linux kernel, Debian, and GNOME. Maemo is based on Debian GNU/Linux and draws much of its GUI, frameworks, and libraries from the GNOME project. It uses the Matchbox window manager, and the GTK-based Hildon as its GUI and application framework.
The UI in Maemo 4 is similar to many handheld interfaces, and features a "Home" screen, which acts as a central point from which all applications and settings are accessed. The Home Screen is divided into areas for launching applications, a menu bar, and a large customisable area that can display information such as an RSS reader, Internet radio player, and Google search box.
The Maemo 5 UI is slightly different: The menu bar and info area are consolidated to the top of the display, and the four desktops can be customized with shortcuts and widgets.
At the Mobile World Congress in February 2010, it was announced that the Maemo project would be merging with Moblin to create the MeeGo mobile software platform.

webOS

Palm webOS is Palm's flagship mobile operating system running on the Linux kernel.
The Palm Pre smartphone was the first device to launch with webOS, and both were introduced to the public at the Consumer Electronics Show in Las Vegas on January 8, 2009 (2009-01-08). The Palm Pre and webOS were released on June 6, 2009 (2009-06-06). The second device to use the operating system, the Palm Pixi, was released on November 15, 2009. The webOS features significant online social network and Web 2.0 integration.

webOS's graphical user interface is designed for use on devices with touchscreens. It includes a suite of applications for personal information management and makes use of a number of web technologies such as HTML 5, JavaScript, and CSS.Palm claims that the design around these existing technologies was intended to spare developers from learning a new programming language.The Palm Pre, released on June 6, 2009, is the first device to run this platform. Devices currently running webOS include the Palm Pre and Palm Pixi on Sprint, and the "Plus" versions that run on Verizon Wireless and AT&T.

Windows Mobile

Windows Mobile  is a mobile operating system developed by Microsoft for use in smartphones and mobile devices. The current version is called "Windows Mobile 6.5". It is based on the Windows CE 5.2 kernel, and features a suite of basic applications developed using the Microsoft Windows API. It is designed to be somewhat similar to desktop versions of Windows, feature-wise and aesthetically. Additionally, third-party software development is available for Windows Mobile, and software can be purchased via the Windows Marketplace for Mobile.
Originally appearing as the Pocket PC 2000 operating system, most Windows Mobile devices come with a stylus pen, which is used to enter commands by tapping it on the screen. Microsoft announced a completely new phone platform, Windows Phone 7, at the Mobile World Congress in Barcelona on February 15, 2010. Phones running Windows Mobile 6.x will not be upgradeable to version 7.